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Author Topic: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x  (Read 56044 times)

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Offline zlymex

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Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« on: September 28, 2016, 09:39:32 PM »
Brief facts
 - 2DW23x series is a Chinese brand temperature compensated Zener reference
 - There are two identical zener diodes connected in back to back manner in a 3-lead TO-39 package.

 - Norminal voltage 6.0V t0 6.5V
 - Norminal zero-TC current ranges from 5mA to 15mA depending on types.
 - Datasheet(in Chinese) http://www.chinaeds.com/zl/%E5%B8%B8%E7%94%A8IC%5C2%5C2D%5C2DW230.pdf

Why 2DW23x
These 2DW23x series(2DW232, 2DW233, 2DW234, 2DW235) has been around for many year and was probably the only 'reference grade' zener in China. Previously known as 2DW7C and changed name about ten years ago. There were/are many manufacturers making these devices and I have tons of them. The performance varies according to makers very much and generally are poor (aging rate, tempco, noise). I've never use them in my designs/circuits.

However, people discovered that there is this Shanghai 17th Radio Factory making this particular Diamond brand(there is a diamond symbol on face of each device) with exceptional low noise, even lower than that of LTZ1000. I didn't believed, but there are a lot of buying/teardown/discuss about it:
http://bbs.38hot.net/forum.php?mod=viewthread&tid=49306
http://bbs.38hot.net/forum.php?mod=viewthread&tid=84620
http://bbs.38hot.net/forum.php?mod=viewthread&tid=119921
http://bbs.38hot.net/forum.php?mod=viewthread&tid=120264
http://bbs.38hot.net/forum.php?mod=viewthread&tid=120731

So, I built my own noise meter recently and bought some samples. At first, the noise tested is not good, 1.2uVp-p, same or slightly inferior to LTZ1000. However, some one soon pointed out that the power supply might be the problem. After I changed the power source to batteries, I got even better result than others: 0.4uVp-p at 5mA, which is one third of LTZ1000. I swapped devices, altered current, measured my other LTZ1000 based voltages(4910, 732A, 732B etc) as reference, and I bought more 2DW23x from other e-stores, they all show this ultra-low noise characteristic.


Availability
I bought about 200 unit of 2DW233 from here: https://item.taobao.com/item.htm?spm=a1z09.2.0.0.gpf2Zk&id=35815633601

Then I bought 550 unit of 2DW234 from another seller.

There are many sellers at Aliexpress selling these cheaply but only buy those with diamond mark on the top such as
http://www.aliexpress.com/item/Free-shipping-2DW233-DIP3/32433963421.html
http://www.aliexpress.com/item/hot-spot-10pcs-2DW232-new-original-in-stock/32637084815.html
https://www.aliexpress.com/item/High-quality-10Pcs-2DW234-2DW235-2DW236-New/32527935820.html
Be warned, I got these links by searching only. Someone was buying one of the entries and did not receive the package in 75 days.


My plan to test/use
1. A very simple circuit(batteries+resistor) to test/verify noise, done.

2. A simple circuit to test/seek the zero-TC point, partially done.
For a given device at given zener current, there is a convex shape of voltage-temperature curve and there is a peak voltage which is the zero-TC point for temperature.

Because of this, for a given device at given temp, there is a convex shape of voltage-current curve and there is a peak voltage which is the zero-TC point for zener current.
The type number(2DW232, 2DW233) indicating different nominal zener current for this zero-TC point. For instance, the zero-TC current of 2DW232 is 5mA, the zero-TC current of 2DW233 is 7.5mA, the zero-TC current of 2DW234 is 10mA, and so on.
But in reality,  there is not much difference. A device of any type may show zero-TC current at any value ranging from 4mA to 20mA, therefore, there is need to test every device for it's zero-TC current.

3. Accelerate aging
Boil at 100 degree C and freeze at -15 degree C, repeat the cycle many times.

4. A circuit to test aging rate etc.
 - build many to test simultaneously
 - characterize TC
 - test by continuous power up, power down/up, mild thermal shock, mechanical shock

The zener current(5mA to 10mA) is supplied by an foil resistor R1 from the final 10V. The current should be stable to 25ppm annually.
R2 and R3 are foil divider pair, the exact value is no very important but this 10V should be stable to 15ppm annually(assuming 2DW233 is stable).
I'll use AD707AH because I have a lot of them and the noise is not too bad(0.23uVpp, 14pAp-p).

5. Others
I've built one prototype but the noise is not as low as expected probably because there is no heat sink/thermal lag.



Reference
There is a Chinese military standard SJ 50033/150-2002 on 2DW230-2DW236.
http://doc.mbalib.com/view/7ff38949056ec076fcf871d4e67ec0f4.html


More datasheet from the industry
http://doc.mbalib.com/view/1a1945b2dcc8911e2a82b0f5ff52fc0f.html

I also found an old article(dated 1986, attached but in Chinese), the author were obviously from Shanghai 17th radio factory describing this 'superb' zener of Diamond brand.
He said, from 1982, the factory began a profound revolutionary change of the process structure of the 2DW230-2DW236 series making it rival similar products abroad in term of low noise and low drift. There are some test results in the article but the author did not tell anything about their new process. There was someone who tested an 2DW234 dated 1987 and got 3.2uVp-p noise, compatible with what have described in the article(http://bbs.38hot.net/forum.php?mod=viewthread&tid=120264). He also tested another 2DW234 dated 2013 and got 0.57uVp-p noise. This means that there must be another change of the process structure in Shanghai 17th radio factory between 1987 to 2013. One thing for certain is that they changed the internal connection of two zener from common anode(as can be seen from above two internal diagrams) to common cathode.

I took apart one(of 2DW234), here is the photo by my card camera plus a magnifier

Someone at 38hot(archwang) took a much better inside photo of 2DW234 dated 2013(see attached)
« Last Edit: September 29, 2016, 03:30:08 PM by zlymex »
 
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Offline zlymex

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #1 on: September 28, 2016, 09:42:44 PM »
Low frequency noise test
By my DIY noise meter(http://www.eevblog.com/forum/metrology/diy-low-frenquency-noise-meter/), I tested some 2DW233.



For a given zener, the LF noise is inverse proportional to the square root of applied current. I plotted the curve for some well known zeners with 2DW23x which shows 2DW232 is about 2.54 times better noise wise or 6.5 times better current wise.



T.C. test



Aging test
« Last Edit: September 29, 2016, 01:41:32 AM by zlymex »
 

Offline Kleinstein

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #2 on: September 29, 2016, 01:29:06 AM »
With the two references in one case one could use the second zener as a normal diode to sene the chip temperature.

Form the internal pictures shown in one of the links, it looks like the chip itself is covered in a drop if transparent glue (e.g. epoxy). So heating to more than 100-120 C (and the speed of cooling from there) might have an influence on the glue and thus performance / aging.

With the relatively high power, there can be temperature fluctuation due to turbulent air flow - this might look very much like 1/f noise. Often one covers sensitve circuits with a kind of foam / fiber.
 
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Offline zlymex

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #3 on: September 29, 2016, 01:52:27 AM »
With the two references in one case one could use the second zener as a normal diode to sene the chip temperature.

Form the internal pictures shown in one of the links, it looks like the chip itself is covered in a drop if transparent glue (e.g. epoxy). So heating to more than 100-120 C (and the speed of cooling from there) might have an influence on the glue and thus performance / aging.

With the relatively high power, there can be temperature fluctuation due to turbulent air flow - this might look very much like 1/f noise. Often one covers sensitve circuits with a kind of foam / fiber.

I think you are absolutely correct on these points. I'm going to design an temperature oven by using the forward biased diode. I also boiled 200 pieces for high temperature cycle but not higher.
 

Offline Cerebus

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #4 on: September 29, 2016, 07:14:20 AM »
All very interesting, thanks for posting this.
Anybody got a syringe I can use to squeeze the magic smoke back into this?
 

Offline quarks

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #5 on: September 29, 2016, 06:00:21 PM »
Bookmark!
Thanks a lot for sharing.
 

Online Nuno_pt

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #6 on: September 29, 2016, 07:18:23 PM »
+1
Nuno
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Offline retrolefty

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #7 on: September 29, 2016, 09:54:38 PM »
Bookmark!
Thanks a lot for sharing.

Ditto  :-+
 

Offline WN1X

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #8 on: September 30, 2016, 12:42:37 AM »
I also boiled 200 pieces for high temperature cycle but not higher.

Zener diode soup...my favorite  :-DD

Very interesting thread...I look forward to future updates  :-+
- Jim
 

Offline Theboel

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #9 on: October 06, 2016, 03:20:56 PM »
Try to contact some seller who offer this Zener but no luck, perhaps some else luckier than me can share information
 

Offline zlymex

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #10 on: October 07, 2016, 03:04:22 AM »
Try to contact some seller who offer this Zener but no luck, perhaps some else luckier than me can share information
1st Oct. to 7th Oct. is a Holiday in China.
 

Online Nuno_pt

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #11 on: October 07, 2016, 07:57:58 PM »
I'll let this next few days pass, because of the back orders that the sellers might have, and next week I'll try to buy some 10 to 30 units and try to make 2 or 3 boards and test over time for drift.
Nuno
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Offline Theboel

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #12 on: October 08, 2016, 12:10:00 AM »
@ Zlymex,
Thank You for the information. but still if anybody outside china can buy it online I like to know the information.

btw, I like to use this zener for discrete ADC/DAC in audio freq range application anyone has experience about that ?
 

Online blueskull

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #13 on: October 08, 2016, 12:20:20 AM »
2DW family... Classic Chinese part numbering, dates back to the 60s/70s. Probably you can build an OPAMP for your new reference with 3AX/3DG transistors >:D, that will be cool, very cool vintage tech porn.
SIGSEGV is inevitable if you try to talk more than you know.
 

Offline ali_asadzadeh

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #14 on: October 14, 2016, 03:57:13 AM »
Zlymex how do you compare 2DW232 with LTZ1000A when you are measuring them with the gears that use LTZ1000A as their reference and claiming that they are better than LTZ1000A also I have another question, how they characterized the LTZ1000A against what beast?
You can order parts from www.ASiDesigner.com
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Offline Squantor

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #15 on: October 14, 2016, 06:08:11 PM »
@ Zlymex,
Thank You for the information. but still if anybody outside china can buy it online I like to know the information.

btw, I like to use this zener for discrete ADC/DAC in audio freq range application anyone has experience about that ?

I ordered at this store: https://www.aliexpress.com/item/2DW230-2DW231-2DW232-2DW233-2DW234/966304921.html

It is still underway to me, hopefully they are the "diamond" brand zeners, a lot of people are using the same pictures. I will report back as soon as I get them. One thing to notice with this vendor is that you need to send him a message with what type you want to buy.
 

Offline VintageNut

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #16 on: October 22, 2016, 04:25:26 AM »
I ordered 30 pcs from the below link. Only 10 pcs arrived

https://www.aliexpress.com/item/High-quality-10Pcs-2DW234-2DW235-2DW236-New/32527935820.html?spm=2114.13010608.0.0.lA0Mcy

The parts arrived but they do not have the diamond mark on top. There is no mark on top. The part number is written in blue on the side with no visible production date. The logo in blue is mostly a blur and not readable.

I have contacted the seller and asked for a refund. I paid $20 for 30 pcs to be sent to me. My guess is that most of these sellers are selling garbage parts with a picture of the good stuff on their page.
« Last Edit: October 22, 2016, 04:45:49 AM by VintageNut »
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Offline JS

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #17 on: October 22, 2016, 06:03:35 AM »
I ordered 30 pcs from the below link. Only 10 pcs arrived

https://www.aliexpress.com/item/High-quality-10Pcs-2DW234-2DW235-2DW236-New/32527935820.html?spm=2114.13010608.0.0.lA0Mcy

The parts arrived but they do not have the diamond mark on top. There is no mark on top. The part number is written in blue on the side with no visible production date. The logo in blue is mostly a blur and not readable.

I have contacted the seller and asked for a refund. I paid $20 for 30 pcs to be sent to me. My guess is that most of these sellers are selling garbage parts with a picture of the good stuff on their page.

Even if they are doing that makes no sense to not send the specified quantity...

JS
If I don't know how it works, I prefer not to turn it on.
 

Offline VintageNut

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #18 on: October 22, 2016, 08:16:43 AM »
I ordered 30 pcs from the below link. Only 10 pcs arrived

https://www.aliexpress.com/item/High-quality-10Pcs-2DW234-2DW235-2DW236-New/32527935820.html?spm=2114.13010608.0.0.lA0Mcy

The parts arrived but they do not have the diamond mark on top. There is no mark on top. The part number is written in blue on the side with no visible production date. The logo in blue is mostly a blur and not readable.

I have contacted the seller and asked for a refund. I paid $20 for 30 pcs to be sent to me. My guess is that most of these sellers are selling garbage parts with a picture of the good stuff on their page.

Even if they are doing that makes no sense to not send the specified quantity...

JS

I stand corrected. The other 20 pcs were balled up in what looked like filler packing. So they did send all 30 but these are not what is pictured. Many of the sellers of these have the same picture posted.

I picked a different seller and sent an email asking if the parts are exactly as pictured. We shall see what happens. No big deal one way or the other. It would be good to get 20 to 30 of these and let a batch cook for a while.
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Offline zlymex

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #19 on: October 22, 2016, 01:08:13 PM »
That's very unfortunate @VintageNut. Anyway, only the diamond brand has low noise property, others are just garbage.
 

Offline martinr33

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #20 on: October 22, 2016, 05:31:18 PM »
I have managed to get some via TaoBao. They look genuine.  I'll see if I can persuade my wife to put them up for sale on her web site.




 

Offline Kleinstein

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #21 on: October 22, 2016, 06:39:46 PM »
Are there data on how good those references are in respect to drift. The kind of glue on top of the chip is not that promising, as it might age, especially at higher temperature.
 

Offline janode

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #22 on: October 22, 2016, 09:13:29 PM »
I tried my luck with "AIX ELECTROINC CO.,LTD":
https://www.aliexpress.com/item/2DW233-DIP3/32354191799.html

Oh well, not so surprisingly the components don't look the same as in the picture. There's poor quality blue printing on the side, not the top, of the components. Leads are gold colour.. actually very close to colour of my 21K gold ring. Weird if they bothered to waste actual gold on those  :-DD. I would love to add here the head banging smiley, because it's so great, but I'm not really disappointed.
 

Offline VintageNut

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #23 on: October 22, 2016, 10:28:30 PM »
I have managed to get some via TaoBao. They look genuine.  I'll see if I can persuade my wife to put them up for sale on her web site.


That would be cool and very helpful.
How did you purchase via Taobao? I could not get the website to be usable in english.
« Last Edit: October 22, 2016, 10:30:29 PM by VintageNut »
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Offline SeanB

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #24 on: October 22, 2016, 10:57:10 PM »
I tried my luck with "AIX ELECTROINC CO.,LTD":
https://www.aliexpress.com/item/2DW233-DIP3/32354191799.html

Oh well, not so surprisingly the components don't look the same as in the picture. There's poor quality blue printing on the side, not the top, of the components. Leads are gold colour.. actually very close to colour of my 21K gold ring. Weird if they bothered to waste actual gold on those  :-DD. I would love to add here the head banging smiley, because it's so great, but I'm not really disappointed.

My bet is they simplt relabelled old stock transistors and sold them. Try them for gain, it might be a Germanium PNP transistor with a badge job.
 

Online Nuno_pt

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #25 on: October 22, 2016, 11:03:46 PM »
For those interested in the 2DW2xx, maybe zlymex can help out, since he has access to tabao and know's what could be real, we could buy them for the ones that want them, and send them out, if he want to get this kind of trouble. :-)
Nuno
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Offline zlymex

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #26 on: October 23, 2016, 01:17:20 AM »
For those interested in the 2DW2xx, maybe zlymex can help out, since he has access to tabao and know's what could be real, we could buy them for the ones that want them, and send them out, if he want to get this kind of trouble. :-)

Yes. I can buy a batch and mail it to one oversea location at my own expense, and the one who receive the package will responsible for distribution to who ever needed and agreed in certain term.
 
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Offline VintageNut

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #27 on: October 23, 2016, 02:45:28 AM »
Hello Zlymex

That would be a "group buy" as we say in the USA.

I am willing to host the logistics in the USA. I can receive the parts and send out the parts to the participants in the USA.

For myself, I do not require hundreds of parts. I only need 20 to 30 pcs of each of 2dW233, 2dw234.

Do the higher current parts have lower noise? For example does the 2DW234 have lower noise than the DW233? If so, is the 2DW236 the lowest noise part?
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Offline Cerebus

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #28 on: October 23, 2016, 03:53:52 AM »
Is there any particular place in Europe that would be advantageous from a postal costs point of view to use as a hub for the European leg of this? I ask as I'm quite happy to volunteer as the hub of the European leg of this, but UK postal rates to other European countries have always traditionally been one of the higher.
Anybody got a syringe I can use to squeeze the magic smoke back into this?
 

Offline zlymex

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #29 on: October 23, 2016, 03:51:24 PM »
Ok. may be I will buy 200pcs(or more?) and mail them to VintageNut/USA, and VintageNut will mail 100pcs to Cerebus/Europe, or may be the other way round. I'll check which way is better(available postal, custom, pricing) tomorrow.

From my tests, 2DW232 or 2DW233 will do, the difference with others(2DW235, 2DW234) is only the nominal zero TC current, but I saw not very much actual difference, and the zero TC current of 2DW232 or 2DW233 are usually higher than nominal. The manufacture seems to mark the brand randomly.
 

Offline JS

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #30 on: October 23, 2016, 04:17:50 PM »
  You do want zero TC, if it's at higher current it would usually be a good thing, as it means lower noise, unless you are after long term stability instead of low noise, in which case you wouldn't be using the 2DW233 I guess.

JS
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Offline Kleinstein

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #31 on: October 23, 2016, 08:09:47 PM »
Even the 2DW233 has the zero TC at already quite a high current level and thus low noise. High currents also cause more self heating and thus require a higher temperature. So I don't think it really helps to go above 5 mA. If than one could still use 2 units in parallel for lower noise - usually 2 units at 5 mA should give a lower noise than 1 at 10 mA, not for the higher frequency part, but for the 1/f part. With the relatively low price it is a very real option to use 2 or even more refs combined.
 

Online Nuno_pt

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #32 on: October 23, 2016, 09:54:42 PM »
This would be a good project to buy some 30 of the 2DW2xx, select 14 of them and make an stable 100V, but probably the PSU's would have to be separate for each, this could be better than buffering the LM399/LTZ to 100V.
Nuno
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Offline Theboel

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #33 on: October 23, 2016, 10:33:34 PM »
count me for 20pcs, EU or USA doesnt matter  8)
 

Offline VintageNut

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #34 on: October 23, 2016, 11:27:31 PM »
Hello Zlymex

The lowest cost will be China Post to United States Postal Service.

I have bought several $20 items from eBay and AliExpress that incur no customs fee to the USA. There is ePacket China Post shipping which is used by eBay that is very low cost.

If you ship to UK or Eu first , there will probably be Value Added Tax.

If it is not too much trouble, maybe ship one package to USA and one package to UK?
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Offline zlymex

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #35 on: October 24, 2016, 12:36:15 AM »
Ok, the item I plan to buy is here: https://item.taobao.com/item.htm?spm=a230r.1.14.17.q4TxU1&id=35862405041
I've already bought from the entry before and proofed to be genuine(low noised). I've just online talked to the seller that they still have the same batch as I bought for at least 300pcs, which is dated 14-4.
 

Offline eliocor

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #36 on: October 24, 2016, 12:45:09 AM »
I would be interested in about 30/50 pieces...
I live in Europe (Italy)
« Last Edit: October 24, 2016, 01:19:59 AM by eliocor »
 

Online Nuno_pt

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #37 on: October 24, 2016, 12:55:12 AM »
If you ship to UK or Eu first , there will probably be Value Added Tax.

Here till 22€ we don't pay nothing, but if the package is small and the value is higher, and the declared value is low e.g. $5 there is no problem.
The prices here for the shipping for all EEC are 4€ till 500g, I can post here the shipping cost for the various weights.
 
If it is not too much trouble, maybe ship one package to USA and one package to UK?

That would be best, since from the US to EU, you can add another week at least.

Nuno
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Offline evb149

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #38 on: October 24, 2016, 12:58:39 AM »
Hi, I would be interested in some in the USA.  Somewhere in the 25-250 range I suppose depending on what the overall pricing looks like.

EDIT: Hi zlymex, thank you for all of the good information you have shared about these models of references as well as noise measurement circuits, and for being willing to facilitate a group buy.
And thank you VintageNut, thank you for your interest to also facilitate a group buy.
I am wondering what the price discount versus quantity of parts purchsed is?  I think I saw that zlymex may have previously been buying hundreds of such parts, (550pcs, 200pcs,...) at once, and maybe that is at the best price per lot level or maybe it is better at some other possible level that is achievable in the group purchase?

Also I apologize for the basic question but I wonder if from the research you all have done if there is any indication as to the likely magnitude of the long term drift of these devices, and also the unit to unit variation of characteristics in a batch, and whether some factors like humidity change, mechanical stress, or vibration would likely be a significant concern in integrating these into a circuit?

In response to VintageNut's comment about a temperature controller, as well as to generalize about making some open HW that could be useful to the users of this part, I would be glad (*as long as I can spare any time in the coming days/weeks) to contribute my effort to design a temperature controller or other accessory PCB / circuit design for this sort of purpose. 

I do not have access to any especially good temperature measurement hardware (beyond basic NTC thermistors, a couple of IC digital sensors, some K thermocouples, and 2N3904 junctions that could be measured), and not at all any premade environmental controlled test / calibration system, though, but I could make a custom firmware + data acquisition based controller design and come up with some ideas for use of either printed foil heaters, discrete resistor heaters, or similar simple concepts.  I suppose that should easily be enough to look for non-absolute temperature correlated short term variations in particular spots of maybe under 0.1C.  I might be able to get a basic RTD to look for smaller fluctuations and have something more closely correlated to absolute temperature.

 
« Last Edit: October 24, 2016, 05:12:40 AM by evb149 »
 

Offline pmcouto

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #39 on: October 24, 2016, 01:01:24 AM »
I would be interested in about 50 pcs.

Regards,
Pedro
 

Offline Squantor

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #40 on: October 24, 2016, 01:48:46 AM »
I would be interested in 20 pieces or more depending on pricing. I live in the Netherlands.

I have actually ordered a bunch from aliexpress. Hopefully they are diamond brand but I don't count on it.
 

Offline JS

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #41 on: October 24, 2016, 02:08:46 AM »
This would be a good project to buy some 30 of the 2DW2xx, select 14 of them and make an stable 100V, but probably the PSU's would have to be separate for each, this could be better than buffering the LM399/LTZ to 100V.

You could do it with a single supply, provided you find the zero TC current for all the devices together.

Even the 2DW233 has the zero TC at already quite a high current level and thus low noise. High currents also cause more self heating and thus require a higher temperature. So I don't think it really helps to go above 5 mA. If than one could still use 2 units in parallel for lower noise - usually 2 units at 5 mA should give a lower noise than 1 at 10 mA, not for the higher frequency part, but for the 1/f part. With the relatively low price it is a very real option to use 2 or even more refs combined.

Ok, when you said require a higher temp are you talking about an oven or just that it will go higher? I should double check the levels, I didn't know it was already that high.

JS
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Offline VintageNut

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #42 on: October 24, 2016, 03:16:13 AM »
Ok, the item I plan to buy is here: https://item.taobao.com/item.htm?spm=a230r.1.14.17.q4TxU1&id=35862405041
I've already bought from the entry before and proofed to be genuine(low noised). I've just online talked to the seller that they still have the same batch as I bought for at least 300pcs, which is dated 14-4.

Hello Zlymex

If you buy 300 pcs, you can ship 150 pcs to USA and 150 pcs to Eu. I can handle sending out envelopes from USA.

My thought is to make 25 pcs available to 5 people from the USA. I will keep 25 pcs for my project(s).

The seller's price at Taobao looks like USD $0.25 each so the 150 pcs will be USD $37.50 plus shipping to Zlymex in China and shipping from China to USA and any customs that the US Customs charges. We shall see.

Zlymex, I can send you payment from Paypal if you want. Just let me know. There is no hurry for me.

My intention is to make one "group reference". Sort of a poor man's bank of Fluke 732B. It would be good to find a way to make an ovenized PCB that can be kept at 30 deg C or maybe even a little higher.

Thank you for sharing your China low noise zener source!
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Online pelule

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #43 on: October 24, 2016, 03:53:02 AM »
I would have interest in 30 pieces for me as one of the European batch receivers.
You will learn something new every single day
 

Offline MatteoX

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #44 on: October 24, 2016, 04:23:30 AM »
Hi, I would also be interested for 25 pcs or more for the USA group buy.
 

Offline Cerebus

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #45 on: October 24, 2016, 04:29:42 AM »

The prices here for the shipping for all EEC are 4€ till 500g, I can post here the shipping cost for the various weights.


As I suspected, that rules out the UK as the European hub. The cheapest from here to Portugal for 250-500g is over £5 GBP - even with the low £ that's still nearly 50%  higher shipping costs.
Anybody got a syringe I can use to squeeze the magic smoke back into this?
 

Online Nuno_pt

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #46 on: October 24, 2016, 04:55:23 AM »
We've also the express mail, that is from 100g - 250g = 4.70€ and from 250g - 500g = 6.40€ for EU.

The normal mail is 100g - 250g = 2.35€ and from from 250g - 500g = 4€ for EU.

And 0.65€ for an bubble bag, so if the 25x 2DW23x are from 100g - 250g, that will be 2.35€ + 0.65€ = 3.00€ + 23% VAT = 3.69€ if my math is correct, and I'm looking at this the correct way.

Let's see how many are need for EU & US.
Nuno
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Offline Cerebus

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #47 on: October 24, 2016, 05:28:46 AM »
We've also the express mail, that is from 100g - 250g = 4.70€ and from 250g - 500g = 6.40€ for EU.

The normal mail is 100g - 250g = 2.35€ and from from 250g - 500g = 4€ for EU.

And 0.65€ for an bubble bag, so if the 25x 2DW23x are from 100g - 250g, that will be 2.35€ + 0.65€ = 3.00€ + 23% VAT = 3.69€ if my math is correct, and I'm looking at this the correct way.

Let's see how many are need for EU & US.

The nearest part, mechanically, I have here is in a TO-72 case and that weighs in at 0.91gm. So 25 off would be in the close region of 25gm + the weight of packaging.
Anybody got a syringe I can use to squeeze the magic smoke back into this?
 

Online Nuno_pt

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #48 on: October 24, 2016, 05:34:28 AM »
Ok so new prices for normal mail;

20g - 50g = 1.20€
50g - 100g = 1.40€

For express mail;

20g - 50g = 3.10€
50g - 100g = 3.60€

Plus the above package and VAT.

Nuno
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Offline evb149

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #49 on: October 24, 2016, 06:25:37 AM »
From the picture it looks like these may (just a guess since they could just be side by side die) be monolithic.
Does anyone know from a tear down or thermal analysis if this is one monolitic die, or two physicaly different die side by side?

Has anyone done a thermal analysis to see what the temperature coupling response is from one zener to the next?

If they are either monolithic or side by side independent die but likely from the same wafer I wonder how good the parametric matching is from one zener to the next in the same package?
 
It seems like one could
(a) make a dual reference of course + and - 6.xV
(b) use the second zener as a forward biased diode junction temperature sensor  to sense temperature of the other zener (as has been mentioned here)
(c) maybe use one zener with a variable curent through it as a heater to heat the adjacent unit and help control its temperature over a small range (and perhaps also as a temperature sensor).
 

Offline orin

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #50 on: October 24, 2016, 06:39:21 AM »
Count me in for 20 in the USA.
 

Offline branadic

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #51 on: October 24, 2016, 07:38:08 AM »
I'm interested in 30 pieces too. Germany/Europe
Prema 5000 | Prema 5017 SC | Tek 2465A | VNWA2.x with TCXO upgrade and access to: Keysight 3458A, Keithley 2002, Keithley 181, Prema 5017 SC, 34401A, 34410A, HDO6054, Keysight 53230A and other goodies at work
 

Offline hammy

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #52 on: October 24, 2016, 07:48:06 AM »
I would also be interested for 30 pcs for the EU/Germany group buy.

Thank you!  :-+
 

Online Nuno_pt

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #53 on: October 24, 2016, 08:22:25 AM »
The price from the link that @zlymex post from tabao shows $0.24 each, plus shipping from @zlymex to both US & EU host's.
The shipping from @zlymex to each host (1 in US, 1 in EU) would be divided by all in each group.
Then each one in that group (US & EU) would pay the shipping from the host to is address to the host.
Also from my point of view makes more sense after @zlymex give the shipping price for each host, and we've close the numbers of the buy, that all should pay directly to @zlymex, leaving that way only the last shipment to pay to the host.

From what I get till now, here are some numbers;

Europe:
@Theboel - 20
@eliocor - 30 (Buy Limit)
@pmcouto - 30 (Buy Limit)
@Squantor - 30 (Buy Limit)
@pelule - 30
@branadic - 30
@hammy - 30
@ Nuno_pt - 30
@Cerebus - 20
@manganin - 30 (Buy Limit)
@2N3055 - 20
@MosherIV - 3
@janode - 20
@Alex Nikitin - 30 (Buy Limit)
@babysitter - 30
@plesa - 30



US:
@evb149 - 30 (Buy Limit)
@MatteoX - 30 (Buy Limit)
@orin - 20
@VintageNut - 25
@Galaxyrise - 20

Asia - 20


Anyone missing?

Updated & Buy Limit impose to 30 for person, because of the explanation below given by @zlymex, after this there could be organize another group buy for those that need more parts, but this propose is to try the 2DW23x series for drift beside the LM399/LTZ1k.

Updated
« Last Edit: October 25, 2016, 06:38:57 PM by Nuno_pt »
Nuno
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Offline Cerebus

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #54 on: October 24, 2016, 08:48:45 AM »
Put me down for 20 or whatever turns out to be the nearest convenient quantity.
Anybody got a syringe I can use to squeeze the magic smoke back into this?
 

Offline manganin

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #55 on: October 24, 2016, 08:51:42 AM »
200 pcs / EU
 

Offline 2N3055

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #56 on: October 24, 2016, 09:19:45 AM »
Can I have 20 pcs/EU please?
 

Offline martinr33

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #57 on: October 24, 2016, 09:54:04 AM »
Mine came from here:

https://world.taobao.com/item/35862405041.htm?fromSite=main

I think that is the same supplier. The ones I have have a colored dot on the side, and a black diamond logo, part number and date code on the top. One batch is 2016, the others are 2015.

I opened a couple up, they have a white silicone seal not an epoxy seal. I'll try to get the silicone off, get some pictures.
 

Offline zlymex

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #58 on: October 24, 2016, 10:36:49 AM »
Well, that amount(summarized by Nuno_pt) certainly exceed my expectation.
Like I said, I'll buy 200-300 pcs and ship to one oversea location(USA) at my own expense.
The purpose of the 'group buy' from my point of view is for test for EEVBLOG members, therefore I hope not exceed 20-30 pcs each.
The reason for the limit is the availability from one seller, also because of the customs here which may have very strict rule for random packages.
Again, This zener has the best noise property I've ever tested, but the T.C. is just average, and drift is a question mark.
 

Online blueskull

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #59 on: October 24, 2016, 10:41:16 AM »
also because of the customs here which may have very strict rule for random packages.

I think customs only cares about incoming packages, not outgoing packages.
SIGSEGV is inevitable if you try to talk more than you know.
 

Offline zlymex

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #60 on: October 24, 2016, 11:01:50 AM »
The price from the link that @zlymex post from tabao shows $0.24 each, plus shipping from @zlymex to both US & EU host's.
The shipping from @zlymex to each host (1 in US, 1 in EU) would be divided by all in each group.
Then each one in that group (US & EU) would pay the shipping from the host to is address to the host.
Also from my point of view makes more sense after @zlymex give the shipping price for each host, and we've close the numbers of the buy, that all should pay directly to @zlymex, leaving that way only the last shipment to pay to the host.

From what I get till now, here are some numbers;

Europe:
@Theboel - 20
@eliocor - 30 to 50
@pmcouto - 50
@Squantor - 20 or more
@pelule - 30
@branadic - 30
@hammy - 30
@ Nuno_pt - 30
@Cerebus - 20
@manganin - 200


US:
evb149 - 25 to 250
MatteoX - 25 or more
orin - 20


Anyone missing?
Thanks very much for the plan and summery. One reason(the expense on me) is that I have difficulty in receiving money from where I reside.
There is no worry thought for this zener to sold out even the group test results are positive because the zener is in production.
The there one slight worry though, the quality may vary among batches. The taobao link I posted is the one which I've tested and proofed to have low noise.

The reason I bought 550pcs of 2DW234 from another seller is because one of my friends bought some samples before and tested to have narrow distribution of zero TC current. The seller got 1100 pcs and we bought them all. These 2DW234 were dated 13-2(Feb 2013) and we cannot find any others seller selling the same thing. New devices, although low in noise, they tends to have large(but similar) distribution of zero TC current, regardless of the part number.
 

Online blueskull

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #61 on: October 24, 2016, 11:07:25 AM »
One reason(the expense on me) is that I have difficulty in receiving money from where I reside.

Or they can pay me to my PayPal or WellsFargo account, then I can transfer money to you in CNY from my SPDB account.
I live in US and I have both US and Chinese bank accounts.
SIGSEGV is inevitable if you try to talk more than you know.
 

Offline Cerebus

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #62 on: October 24, 2016, 11:54:43 AM »
also because of the customs here which may have very strict rule for random packages.

I think customs only cares about incoming packages, not outgoing packages.

Not Chinese customs. They clear outbound packages too. When I order things from China that come with tracking codes I often explicitly see the step in the tracking details. For example, from an order that's currently in transit:

09-Oct-2016 09:41   Departure export customs   SHENZHEN

For the most part they seem to go into export customs and come straight out again, but I've had orders that have sat in Chinese export customs for several days.
Anybody got a syringe I can use to squeeze the magic smoke back into this?
 

Offline Cerebus

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #63 on: October 24, 2016, 11:56:57 AM »
One reason(the expense on me) is that I have difficulty in receiving money from where I reside.

Or they can pay me to my PayPal or WellsFargo account, then I can transfer money to you in CNY from my SPDB account.
I live in US and I have both US and Chinese bank accounts.

This is how people end up in 'extended screening' at the air port. The NSA connect you to a series of payments that take a circuitous route via a Chinese bank account...  ;)
Anybody got a syringe I can use to squeeze the magic smoke back into this?
 

Online blueskull

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #64 on: October 24, 2016, 11:57:49 AM »
Not Chinese customs. They clear outbound packages too. When I order things from China that come with tracking codes I often explicitly see the step in the tracking details. For example, from an order that's currently in transit:

09-Oct-2016 09:41   Departure export customs   SHENZHEN

For the most part they seem to go into export customs and come straight out again, but I've had orders that have sat in Chinese export customs for several days.

I meant Chinese customs does not seize or check outgoing packages, but of course, a package will have to go through customs before entering or leaving China.
SIGSEGV is inevitable if you try to talk more than you know.
 

Offline evb149

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #65 on: October 24, 2016, 12:04:12 PM »
Thanks zlymex, I appreciate all the information you have shared on your noise reference experiments and noise tester circuit. 

I did not intend to ask for too many pieces for convenience of a group buy.  I had just assumed that after seeing your talks of ordering 550 and hundreds more that those were usual lot quantities and perhaps also were less expensive in such quantities as well.

I think some number from a few up to 30 is good for testing for me as you've suggested. 
I was interested in Nuno_pt's idea to use more than 14 in series to achieve a 100V low noise reference, or the idea others have mentioned to use several in parallel to reduce random noise by square root (number) or similar ideas so I thought I could eventually use more than 100 if they worked at least reasonably well.  But I have no urgent short term need to do more than testing with less quantities.

A particular concern to me about finding that a small number of these are good (low noise even if drift is more than TI/Analog/Linear/Maxim similar high grade references) is that it may be hard to order the Shanghai 17th Radio Factory's "good model" part since mostly resellers seem to sell the "junk" versions even accompanied with pictures and specifications of the "good model" part.  So there is temptation to "get the right one while it is clear how to do so".

Another concern is to find that there is some quality of a particular batch of them that is good and not being able to find similar units in the future or from different suppliers so therefore the characterization work could be much harder if trying to characterize different batches ordered over time vs. one batch that may be more consistent.  Though I see that you say that it is not your recent experience that the recently available batches are very consistent in parametric spreads anyway.  But at least we know that the model is good if not the characteristics as tight as the best 2013 batch you found.

And of course that it is hard (so I have seen from others comments, this would be my first try if I should attempt it for this) and maybe expensive depending on the seller's desire to ship internationally in some way to buy from Taobao directly and get the items shipped to the USA for a non-Chinese speaking customer.  But I saw another comment from a different thread that maybe it is easier than it once was to order internationally from Taobao.  If it is not so hard / costly then I and I suppose others would not mind to just order individually if wanting more quantities.
I will see what I can learn about using Taobao.  If the "e packet" low cost shipping service is available easily for US customers and there are no significant other problems/costs for ordering/shipping per order then maybe USA customers could order without causing inconvenience to you.
http://www.eevblog.com/forum/chat/why-use-taobao/msg953114/#msg953114
http://www.eevblog.com/forum/chat/why-use-taobao/msg953118/#msg953118
 
I guess that it is not known that the Shanghai 17th Radio Factory sells these parts "directly" through Taobao / similar markets in low (hundreds) quantities directly to consumers if this particular Taobao seller might not be expected to have such quantities of stock and perhaps could even eventually substitute other factories / models of parts if they run out of this batch?  It seems like they might do some good business with US and European customers if they somehow sold easily via paypal / ebay / whatever.  My own interest is as an aspiring novice volt-nutter but I'd guess it'd be popular for audio enthusiasts and such.

I also noticed that some people (who I have never done any business with so I just mention the messages I have seen in searching for keyword taobao here for my own education about buying from it) say they routinely export items from China to sell through eBay so if demand exceeds what is convenient to arrange for a small group buy I guess someone who routinely sells through ebay might agree to carry this part in their ebay store if they can source the "good version" from the Shanghai 17th Radio Factory or other acceptably certain reseller.  Franky, Tayda, maybe even someplace like Adafruit, Sparkfun, or similar might source / sell such a thing.
http://www.eevblog.com/forum/chat/what-site-to-use-for-puchasing-china-stuff-at-eu/msg176762/#msg176762
 

Offline VintageNut

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #66 on: October 24, 2016, 12:08:01 PM »
The price from the link that @zlymex post from tabao shows $0.24 each, plus shipping from @zlymex to both US & EU host's.
The shipping from @zlymex to each host (1 in US, 1 in EU) would be divided by all in each group.
Then each one in that group (US & EU) would pay the shipping from the host to is address to the host.
Also from my point of view makes more sense after @zlymex give the shipping price for each host, and we've close the numbers of the buy, that all should pay directly to @zlymex, leaving that way only the last shipment to pay to the host.

From what I get till now, here are some numbers;

Europe:
@Theboel - 20
@eliocor - 30 to 50
@pmcouto - 50
@Squantor - 20 or more
@pelule - 30
@branadic - 30
@hammy - 30
@ Nuno_pt - 30
@Cerebus - 20
@manganin - 200


US:
evb149 - 25 to 250
MatteoX - 25 or more
orin - 20


Anyone missing?


25 pcs for me. If Zlymex ships to me, I will ship to the other people in the US. I can also ship USPS to Indonesia. I have Paypal and I can receive the shipping fees. I have participated in sharing components on Diyaudio.com  These parts will go fast.

If Zlymex can only get 300 pcs, there will not be an ability to send 200 pcs to anyone. Everybody be realistic about how many of these parts are available.

The idea is for people to try these Zeners to see if they are lower noise and can work as a reference for DIY metrology at home.

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Online blueskull

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #67 on: October 24, 2016, 12:12:46 PM »
This is how people end up in 'extended screening' at the air port. The NSA connect you to a series of payments that take a circuitous route via a Chinese bank account...  ;)

I have my PhD work in a sensitive field, high density power packaging, which is ITAR controlled, and I receive funding from USDOE plus my lab has connection with USDOD/LMCO. Needless to say, I should have already been tagged.
SIGSEGV is inevitable if you try to talk more than you know.
 

Online MosherIV

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #68 on: October 24, 2016, 05:52:24 PM »
Hi

Can I have 2 or 3 peices please?

Thanks
 

Offline zlymex

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #69 on: October 24, 2016, 06:15:51 PM »
Thank everyone for the info/suggestions/comments.

Initially in this post, I just share some information, providing aliexpress.com(same boss as taobo) links, because I know many people buy electric parts there even with free shipment. Then I heard some bad news that they didn't ship or wrong parts, plus Nuno_pt suggest me to help, that's when I came in.

I've just asked our company's postal office that there is only one postal company to mail to USA, which is EMS China, although the price is high(240 RMB for 500g), I can cope with that. I've never heard ePacket, may be I've never mail anything abroad, may be that service is not available to my area, may be I didn't ask other places.

I'm buying 2DW232 from taobao now, the data code is 15-4, for which I've bought and tested before.

If everything is Ok(my spot check, postal, tests by recipients), and anyone need large quantity, a real group buy can be start later. But if that is still by me/taobao, I will again buy small samples first.

Again, this is a trial at my expense, I don't have any connections with the seller at taobao or the 17th radio factory. If anyone need some piece of 2DW232 for test, leave your comments here, my intention is to get more people involved in testing. For those who have said needing more than 30 pcs, lets see if there are something left.
« Last Edit: October 24, 2016, 06:25:46 PM by zlymex »
 
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Online blueskull

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #70 on: October 24, 2016, 06:23:00 PM »
I've never heard ePacket, may be I've never mail anything abroad, may be that service is not available to my area, may be I didn't ask other places.

ePacket is China Post's special service only offered to professional exporters. For instance, if you constantly ship abroad with an export license, you can get an ePacket account.
SIGSEGV is inevitable if you try to talk more than you know.
 

Online Nuno_pt

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #71 on: October 24, 2016, 09:11:53 PM »
Post with quantities updated above, because of this Zener is still in production and can be bought in another group buy with the help from @zlymex, and also because of what @zlymex explain above, the limit will 30 pieces for each person, at a later stage another group buy can be organize and the ones that want more can buy on the second round.

This small quantities of 30 is to choose the best's and to make some PCB's, and look at the comparison about drift in relation to the more use Zeners like LM399/LTZ1k, and see if they can be use also for references in a home lab.

240RMB is 33€ at today exchange, for the EU group with the current committed members the shipping cost from @zlymex to the EU host is 33€/11 members = 3€ each members + ~0.24€ each Zener + shipping from the EU host to each one.

So for 30 pieces that will be 0.24€ each x 30 pieces = 7.20€ + 3€ shipping from @zlymex to EU = 10.20€, plus the shipping from the host to each.
Nuno
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Offline manganin

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #72 on: October 24, 2016, 09:20:28 PM »
200 pcs / EU

My new 100 input scanner will be ready soon. Or actually two of them.

The seller's price at Taobao looks like USD $0.25 each

Cheap enough for a statistical experiment. If available in large quantity...
 

Online Alex Nikitin

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #73 on: October 24, 2016, 09:48:34 PM »
Count me in for 50 pieces.

Cheers

Alex
 

Offline janode

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #74 on: October 25, 2016, 02:42:43 AM »
 

Offline babysitter

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #75 on: October 25, 2016, 03:03:02 AM »
If not too late, i will take 30 pcs too.
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Offline BravoV

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #76 on: October 25, 2016, 03:06:42 AM »
Me 20

Offline janode

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #77 on: October 25, 2016, 03:07:13 AM »
My bet is they simplt relabelled old stock transistors and sold them. Try them for gain, it might be a Germanium PNP transistor with a badge job.

I'm too young for germanium transistors  :-DD I measured Vf 0.7V so silicon. Vz ~5.6V @ 5mA. It would have been more fun to find out they were something weird rebadged, but no..
 

Offline Cerebus

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #78 on: October 25, 2016, 03:12:57 AM »
I'm too young for germanium transistors  :-DD I measured Vf 0.7V so silicon. Vz ~5.6V @ 5mA. It would have been more fun to find out they were something weird rebadged, but no..

I'm old enough to remember scraping the paint off the outside of glass encapsulated OC71s to convert them into phototransistors.  :(
Anybody got a syringe I can use to squeeze the magic smoke back into this?
 

Offline Echo88

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #79 on: October 25, 2016, 05:21:42 AM »
Can someone tell me, how all of you are gonna make use of the low noise while maintaing extremely low drift? Wouldnt it be more reasonable to just stick together a few LTZ1000 to get sqrt(n) noise reduction, while having a very low drift, backed by decades of experience?  ???
 

Online Nuno_pt

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #80 on: October 25, 2016, 05:22:34 AM »
Update, just missing @BravoV since I can't see is flag.

For now:

383 for EU.
115 for US.
20 for Asia.


Let's see how many @zlymex was able to buy,  and then figure a way to split them if enough for all at same time, or we've to buy the rest on the second round.

For now also if put only 30 pieces for each one, base on the 300 units that @zlymex told.
« Last Edit: October 25, 2016, 06:41:25 PM by Nuno_pt »
Nuno
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Online Nuno_pt

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #81 on: October 25, 2016, 05:33:21 AM »
Can someone tell me, how all of you are gonna make use of the low noise while maintaing extremely low drift? Wouldnt it be more reasonable to just stick together a few LTZ1000 to get sqrt(n) noise reduction, while having a very low drift, backed by decades of experience?  ???

On the first page @zlymex show that the 2DW23x has lower noise then the LTZ, but what we'll see is the long time drift, if it's something like the LTZ with can be good since for let's say 4 modules it cost around $1 plus shipping, while the same 4 LTZ it's $200 plus shipping.

For me will be an experiment about long time drift.
Nuno
CT2IRY
 

Offline plesa

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #82 on: October 25, 2016, 05:36:32 AM »
Count me in, please. 30pcs (buy limit)
 

Offline TiN

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #83 on: October 25, 2016, 05:40:28 AM »
Subbed  :popcorn:
xDevs.com | Have test gear documentation to share? Upload here! No size limits, firmware dumps and teardown photos welcome.
 

Offline Galaxyrise

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #84 on: October 25, 2016, 08:04:47 AM »
I'd like to be in for 20.  Very much appreciate the efforts of those members making this possible, even if I'm in too late for this time around.
I am but an egg
 

Offline evb149

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #85 on: October 25, 2016, 12:41:15 PM »
I couldn't get the translate to work for my browser on Taobao last night and I didn't see any indication of Shanghai 17th radio factory online by any searching that I thought could lead to something like a direct alibaba or ebay or tmall store of theirs if they had one.

So for the moment I will be content with whatever quantity is possible to make available in this small group purchase and if there is in the near future another another group buy with larger quantities I would probably still be interested in 100-200 additional pieces of the part discussed here.

If the noise is as good as has been suggested by others' experiences then that to me is good enough to be useful.  If the long term drift is also reasonably low then that is even better.  But for many applications just a somewhat stable but low noise and inexpensive source could be useful for short term measurements.  At 1/200th the cost of a LTZ1000 it would be tempting to use it for dozens of applications where I wouldn't use a much higher cost reference simply due to cost.
And if you need low noise and low drift you can always combine a stable reference with this low noise reference in the same system if you can correct for the drift of this reference via a digitally applied offset from the measured value of the stable reference.

 
 

Offline zlymex

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #86 on: October 25, 2016, 02:43:39 PM »
I bought 9 bags, 450pcs(50pcs in a bag). I have to open at least one bag to check when arrived today or tomorrow.
The weight of one bag is 52.5g, so 9 bags is 473g. Plus package, it may exceed the 500g limit, so I may have to ship 400pcs.

I've just search "2DW232" and "Shanghai 17th Radio Factory"(in Chinese) and got 7 entries, all the sellers are in Shanghai.
The 1st is the one I bought(having bought 5 times), The 2nd have been bought 1 time.

I've once try to put Chinese here but it won't allowed by the forum, but here I try again for Shanghai 17th Radio Factory:
????????

Edit: the above two faces plus two "?" were in Chinese but showed incorrectly.
« Last Edit: October 25, 2016, 02:48:11 PM by zlymex »
 
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Offline TiN

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #87 on: October 25, 2016, 02:46:57 PM »
This forum does not support non-western symbols. Same with cyrillics :)
xDevs.com | Have test gear documentation to share? Upload here! No size limits, firmware dumps and teardown photos welcome.
 

Offline BravoV

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #88 on: October 25, 2016, 02:50:49 PM »
Update, just missing @BravoV since I can't see is flag.

For now:

383 for EU.
115 for US.

Let's see how many @zlymex was able to buy,  and then figure a way to split them if enough for all at same time, or we've to buy the rest on the second round.

For now also if put only 30 pieces for each one, base on the 300 units that @zlymex told.

Check your PM.

Online blueskull

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #89 on: October 25, 2016, 03:02:39 PM »
I've once try to put Chinese here but it won't allowed by the forum, but here I try again for Shanghai 17th Radio Factory:
????????

Put the search URL into a URL shortener, then post the shortened URL.
SIGSEGV is inevitable if you try to talk more than you know.
 

Offline VintageNut

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #90 on: October 25, 2016, 08:07:20 PM »
Hello Zlymex

Can you ship 300 pcs to EU and 150 pcs to USA? There are more people in EU who want these parts.
working instruments :Keithley 260,261,2750,7708, 2015, 236, 237, 238, 147, 220,  Rigol DG1032  PAR Model 128 Lock-In amplifier, Fluke 332A, Gen Res 4107 KVD, 4107D KVD
 

Offline Cerebus

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #91 on: October 25, 2016, 08:58:40 PM »
I've once try to put Chinese here but it won't allowed by the forum, but here I try again for Shanghai 17th Radio Factory:
????????

Edit: the above two faces plus two "?" were in Chinese but showed incorrectly.

The forum software is weird. It manages character encodings correctly up to and including previewing your own comments but then seems to completely stuff the encoding when you actually post the message.

For example, I'll type "?" here, and what's in the quote marks as, I see them, is a Greek omega. I'll hit 'preview' and, it still looks like an omega to me, now I'll hit 'post' and, based on past experience, it'll turn into "?".

Editted to add: And sure enough, that's exactly what happened. It makes the 'preview' feature half useless.
Anybody got a syringe I can use to squeeze the magic smoke back into this?
 

Offline quarks

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #92 on: October 25, 2016, 09:54:05 PM »
seems to be to late, but I would be interested to know if I can still join and buy 30 of it
 

Offline 3roomlab

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #93 on: October 25, 2016, 11:04:51 PM »
- Norminal zero-TC current ranges from 5mA to 15mA depending on types.
These 2DW23x series(2DW232, 2DW233, 2DW234, 2DW235) has been around for many year and ....

were you able to try the diff in noise between the xx2 (5mA) vs the xx5(12.5mA)?
i am trying to prove myself wrong as quickly as possible, then i know for sure, something else is the right answer ... (adapted from richard feynman) ... i am not trolling when i ask stupid questions.
 

Offline zlymex

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #94 on: October 26, 2016, 02:58:25 AM »
- Norminal zero-TC current ranges from 5mA to 15mA depending on types.
These 2DW23x series(2DW232, 2DW233, 2DW234, 2DW235) has been around for many year and ....

were you able to try the diff in noise between the xx2 (5mA) vs the xx5(12.5mA)?
Every device I tested follows the inverse square root rule
Noises were all similar at given current
Zero TC current are different among xx2
Zero TC current are the same between xx2 and xx5
 
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Offline zlymex

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #95 on: October 26, 2016, 03:08:25 AM »
Package arrived today, will test tomorrow.
 
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Offline janode

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #96 on: October 26, 2016, 03:21:00 AM »
Can someone tell me, how all of you are gonna make use of the low noise while maintaing extremely low drift? Wouldnt it be more reasonable to just stick together a few LTZ1000 to get sqrt(n) noise reduction, while having a very low drift, backed by decades of experience?  ???

While low noise and low drift enable many experiments, so does also low cost :) I guess most are hoping this offers a combination of low cost and low noise.
 

Offline evb149

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #97 on: October 26, 2016, 12:14:28 PM »
Thank you very much, zlymex.  It looks good.  Good luck with your tests.
The package seems to have arrived very quickly to you.
 
Package arrived today, will test tomorrow.
 

Offline simon51

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #98 on: October 26, 2016, 02:37:28 PM »
Package arrived today, will test tomorrow.
I also bought 50pcs 2DW232 from the same seller,looking forward your test methods and results. :clap:
 

Offline zlymex

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #99 on: October 26, 2016, 06:31:15 PM »
Package arrived today, will test tomorrow.
I also bought 50pcs 2DW232 from the same seller,looking forward your test methods and results. :clap:

I've just finished testing 10, powered by three lithium cells in series(12.4V noise free) and series 1k precision resistor with the test zener to get about 6.3mA test current.


The terminal marked red(may be other color) is negative, center terminal is positive, the other terminal(connected to the case) open.

Because the noise is very small, and also the TC is not tuned, the device is very sensitive to air turbulence, I covered it with a lot of tissues (wrapped around the device and legs).

The result is positive, 9 is very typical but one is a bit above average. I plotted these on the original chart with added green dots. Some dots are overlapping.

I've packed 430pcs up and ready to ship to VintageNut/USA tomorrow.
« Last Edit: October 26, 2016, 06:33:59 PM by zlymex »
 
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Offline VintageNut

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #100 on: October 26, 2016, 11:51:54 PM »
Hello Zlymex

Thank you for buying these parts for the Metrology community here.
I will coordinate with the other interested people to distribute the parts.
I think we should start a group buy thread and take that discussion off of this thread.

Please let me know if there is a way to compensate you for buying the parts. If you cannot receive an electronic payment, is there something you want to acquire from the USA that I can send to you via USPS/China Post that is the same value? Maybe something that is difficult for you to acquire in China but costs about the same as what you paid for these parts?

The science behind your personal metrology projects is impressive. Building your own microvolt DIY noise meter is one example. For sure, I will want some help on this thread building up a set of 4 references like the Fluke 732B .

best regards,

VintageNut
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Offline Cerebus

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #101 on: October 27, 2016, 01:48:35 AM »
I think we should start a group buy thread and take that discussion off of this thread.

Seconded. The thanks are also seconded.
Anybody got a syringe I can use to squeeze the magic smoke back into this?
 

Offline evb149

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #102 on: October 27, 2016, 10:59:12 AM »
Thank you zlymex.
The results are good to see and interesting.

I've just finished testing 10, powered by three lithium cells in series(12.4V noise free) and series 1k precision resistor with the test zener to get about 6.3mA test current.


The terminal marked red(may be other color) is negative, center terminal is positive, the other terminal(connected to the case) open.

Because the noise is very small, and also the TC is not tuned, the device is very sensitive to air turbulence, I covered it with a lot of tissues (wrapped around the device and legs).

The result is positive, 9 is very typical but one is a bit above average. I plotted these on the original chart with added green dots. Some dots are overlapping.

I've packed 430pcs up and ready to ship to VintageNut/USA tomorrow.
 

Offline hammy

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #103 on: October 27, 2016, 11:26:37 AM »
I've packed 430pcs up and ready to ship to VintageNut/USA tomorrow.

How is the shipping/distribution now organized?

Thank you zylmex!
hammy
 

Offline simon51

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #104 on: October 27, 2016, 02:00:33 PM »
zlymex,thank you!
I do a simple test for 2dw233 compare with ltflu-1.The circuit is same with the fluke5440a REF board that series two sza263(ltflu-1)  then buffer output 13v.I replace ltflu-1 with 2dw233 and series 1.8k(1k should be better) foil resistor with 2dw233 to get current about 3.6mA,then test the output noise(0.1~10Hz),the ltflu-1x2 is about 1.8uV(vpp),the 2dw233x2 is about 1uV(vpp). :-+The problem is the 2dw233x2 output voltage is not stable, The matter needs to bo resolved.

 
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Offline zlymex

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #105 on: October 27, 2016, 02:01:22 PM »
I've packed 430pcs up and ready to ship to VintageNut/USA tomorrow.

How is the shipping/distribution now organized?

Thank you zylmex!
hammy
I've just sent a PM to VintageNut, the shipping company(EMS) requires the telephone number of the receiver.
 

Offline zlymex

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #106 on: October 27, 2016, 02:11:28 PM »
zlymex,thank you!
I do a simple test for 2dw233 compare with ltflu-1.The circuit is same with the fluke5440a REF board that series two sza263(ltflu-1)  then buffer output 13v.I replace ltflu-1 with 2dw233 and series 1.8k(1k should be better) foil resistor with 2dw233 to get current about 3.6mA,then test the output noise(0.1~10Hz),the ltflu-1x2 is about 1.8uV(vpp),the 2dw233x2 is about 1uV(vpp). :-+The problem is the 2dw233x2 output voltage is not stable, The matter needs to bo resolved.

Nice work.
It seems to be some 50Hz noise on the photo of the oscilloscope.
The instability of  2DW233 may result from the air flow around the TO-39 case which can be minimized by fillers of soft and insulated material around 2DW233 and the pins on both side of the PCB. Try tissue first.
 

Offline VintageNut

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #107 on: October 27, 2016, 04:37:17 PM »
I've packed 430pcs up and ready to ship to VintageNut/USA tomorrow.

How is the shipping/distribution now organized?

Thank you zylmex!
hammy
I've just sent a PM to VintageNut, the shipping company(EMS) requires the telephone number of the receiver.

I sent a PM with my phone number. Thank you very much for doing this very kind thing!
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Offline VintageNut

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #108 on: October 27, 2016, 04:48:59 PM »
I've packed 430pcs up and ready to ship to VintageNut/USA tomorrow.

How is the shipping/distribution now organized?

Thank you zylmex!
hammy

We will start a new thread for the group buy if the 2DX233 parts that Zlymex has kindly purchased for the group here on this thread.
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Offline zlymex

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #109 on: October 27, 2016, 04:54:31 PM »
I've packed 430pcs up and ready to ship to VintageNut/USA tomorrow.

How is the shipping/distribution now organized?

Thank you zylmex!
hammy
I've just sent a PM to VintageNut, the shipping company(EMS) requires the telephone number of the receiver.

I sent a PM with my phone number. Thank you very much for doing this very kind thing!
Received and the package is shipped.
 

Offline BravoV

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #110 on: October 27, 2016, 06:32:03 PM »
Zlymex, pls read your PM, regarding zones, I'm alone in my region.  :'(

Offline zlymex

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #111 on: October 27, 2016, 06:50:46 PM »
Zlymex, pls read your PM, regarding zones, I'm alone in my region.  :'(
I read your PM but I'm not sure what you need apart from request 20 samples of 2DW232 for which you can contact VintageNut. I'm here only responsible for shipping to one oversea location(USA).
 

Offline babysitter

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #112 on: October 28, 2016, 06:39:09 PM »
Look what a member of my local Makerspace has drawn for me, will be printed next week and hopefully fits 2DW23X and also TO-99 (LTZ1000). At the club we print with PLA which is not suitable for high temperature, ABS can be printed but it seems to need tighter parameter control or something, so no one there likes to print it. Mounting holes are M2. Will publish STL file. The thick wall will be flled with a air chamber structure by the slicing software, giving better isolation than solid material.

Best regards
Hendrik.


 
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Offline branadic

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #113 on: October 29, 2016, 12:06:23 AM »
I have access to a DLP printer (layer thickness 25µm - 150µm, window size 70 x 40mm² with 1920x1080px, maximum part size  400 x 330 x 200mm³).

I printed a LTZ1000 spacer some months ago using a material called PLASTCure Rigid 10500, but a material called PLASTCure Clear 100 (transparen) is available too.
If there is a bigger interest I could offer such caps for small budget by printing a complete batch of such caps.
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Offline quarks

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #114 on: October 29, 2016, 01:11:13 AM »
Hello branadic,

will these caps fit to the HP3458A A9 LTZ1000 Reference Board?

thanks
quarks
 

Offline babysitter

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #115 on: October 29, 2016, 02:19:35 AM »
@Branadic: If you tell me the hole distance and the location of the nose relative to the holes, I can ask this guy to apply it to his drawing. But i have defined relatively thick walls as I can have some air filled closed holes in the wall then.

We have only a prusa I3 filament printer at the club, dont ask for details, I dont know it - yet.

br
hendrik
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Offline branadic

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #116 on: October 29, 2016, 03:45:51 AM »
I guess it was TiN how published a copy of a LTZ1000 cap, a while ago. Maybe someone wants to check wether this one matches the original used in 3458A?
Otherwise we can use any other design, as long as everyone is fine with the it.
The good think about the printed material is, that you can also cut a thread into the material.
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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #117 on: October 29, 2016, 03:50:50 AM »
Maybe we can arrange a cap that fits the LTZ/LM399/2DW23x, they should be pretty close in terms of dimensions.
Nuno
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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #118 on: October 29, 2016, 05:02:46 AM »
I would add myself to the list of buyers of that cap-print-group, if that fit at least to LTZ1000 and 2DW2xx (thus also to LMx99 - not the H package).
You will learn something new every single day
 

Offline babysitter

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #119 on: October 29, 2016, 05:21:52 AM »
Hey, great response! I guess we can make some of them at the club. But first I'd like to check the measures, try the 2DW when they arrive, my LTZ in the finished reference source is already under a (vacuum port) cap. Distribution is easy with STL files, everyone who wants one only has to find someone to print.



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Offline Flinstone

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #120 on: October 29, 2016, 06:02:27 AM »

Hello - I am interested too - Belgium/Europe

30 pieces (buy limit)

Thank you !
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #121 on: October 29, 2016, 06:37:19 AM »
Hi Flinstone,
use that link below to add yourself to the list (but read hints/instruction first, you'll find, if you scroll up on that page a bit )
See link:
http://www.eevblog.com/forum/metrology/group-buy-of-2dw233-ultra-low-noise-zener-reference/msg1057877/#msg1057877
You will learn something new every single day
 
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Offline branadic

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #122 on: November 01, 2016, 05:38:25 AM »
Quote
@Branadic: If you tell me the hole distance and the location of the nose relative to the holes, I can ask this guy to apply it to his drawing. But i have defined relatively thick walls as I can have some air filled closed holes in the wall then.

Could find the CAD files from TiN:

https://xdevs.com/doc/HP_Agilent_Keysight/3458A/cad/a9_cap_top.STEP
https://xdevs.com/doc/HP_Agilent_Keysight/3458A/cad/a9_cap_bot.STEP

There you can find the hole distance.
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Offline Kleinstein

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #123 on: November 01, 2016, 06:08:17 AM »
The cap will be only a minor detail, and usually different from the one for an LTZ1000, as the zener has no internal heater. So the zener will consume less power and good insulation may not be a good thing.
The more important point might be choosing the circuit. The simple version is something like the one used with a LM399 or LM329: scale to a higher voltage (e.g. 10 V) and than use a resistor to set the current.
 

Offline zlymex

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #124 on: November 01, 2016, 02:11:30 PM »
The cap will be only a minor detail, and usually different from the one for an LTZ1000, as the zener has no internal heater. So the zener will consume less power and good insulation may not be a good thing.
The more important point might be choosing the circuit. The simple version is something like the one used with a LM399 or LM329: scale to a higher voltage (e.g. 10 V) and than use a resistor to set the current.

And because if it, a more 'useful' zener current of 8mA or >12mA can be applied to achieve even lower noise per device than LTZ1000 for which the data sheet only recommend 4mA.

The cap or tissue are useful only to stop the air flow around the device/legs, not for thermal insulation. However, these two are often closely related. One good example is the one used by Datron/Wavetek in their 49xx voltage reference where they use black form plus a metal outer case.

As for the step-up to 10V, yes, there is this circuit of "scale to a higher voltage (e.g. 10 V) and than use a resistor to set the current." on the first page of the thread.
 

Offline Kleinstein

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #125 on: November 02, 2016, 06:01:59 AM »
To take really advantage of the low noise of this reference type, one might want to use a lower noise than the AD707 - even though the AD707 is already quite good. As input bias / current noise is not that critical, something like an OP27 / LT1007 should be OK.

 

Offline branadic

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #126 on: November 02, 2016, 06:14:59 AM »
It would be good to have the second diode directly in use, maybe for some servo temperature controller.
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Offline bertik

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #127 on: November 06, 2016, 08:12:42 PM »
What about using the second zener to reduce noise instead?  Feeding it to a separate opamp and then combining reduces the noise by a factor of 1/sqrt(2). While not much this would give an easy improvement for the price of an extra opamp.

Using it just for temp sensing seems a sacrilege.. that could be easily done by gluing a thermistor on top of it.

-BK
 

Offline Kleinstein

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #128 on: November 06, 2016, 09:22:04 PM »
Even with just one diode used, the noise is already really low - e.g. better than an OP07, OP177 or AD707 which are typical candidates for scaling the voltage. The current to get a low TC is already quite high (e.g 5 mA range) - more current is more of a problem it you don't want the chip to heat up too much.

Having a temperature sensor directly on the chip can really help to stabilize or just measure the temperature.  So I would consider this the more practical use for the second diode.
 
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Offline Tazz

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #129 on: November 06, 2016, 09:31:06 PM »
Kleinstein, I second you for the use of the second diode
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #130 on: November 06, 2016, 10:47:02 PM »
Zlymex:

Isnt the 2nd diode already used forward biased as temperature compensation diode?
I cannot get this clear from your description.
In this case you do not need to think about further noise reduction.

Or are there 2 temperature compensated diodes (2 zeners + 2 diodes) in one package?
In this case you cannot read the temperature. (because the zener voltage is in series to the compensation diode).

with best regards

Andreas
 

Offline plesa

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #131 on: November 06, 2016, 11:33:37 PM »
Zlymex:

Isnt the 2nd diode already used forward biased as temperature compensation diode?
I cannot get this clear from your description.
In this case you do not need to think about further noise reduction.

Or are there 2 temperature compensated diodes (2 zeners + 2 diodes) in one package?
In this case you cannot read the temperature. (because the zener voltage is in series to the compensation diode).

with best regards

Andreas

There are only two zeners, back to back and common anode connected to package.
So there is first order temperature compensation - zener avalanche  diode.
On first piece I will have I'm going to remove epoxy and check it under microscope.
http://www.eevblog.com/forum/metrology/ultra-low-noise-reference-2dw232-2dw233-2dw23x/
It is the same like used in zeners like 1N82x.
« Last Edit: November 06, 2016, 11:35:58 PM by plesa »
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #132 on: November 06, 2016, 11:52:16 PM »
The 1N82x has a normal diode in series to the zener.

with best regards

Andreas
 

Offline plesa

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #133 on: November 06, 2016, 11:59:06 PM »
The 1N82x has a normal diode in series to the zener.

with best regards

Andreas

OK, and do you thin that doping level will make noticeable difference in tempco of forward biased diode?
 

Offline evb149

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #134 on: November 07, 2016, 12:18:28 AM »
I suggest a flexible arrangement to use the second diode --
(a) To be able to use it forward biased to measure temperature. 
(b) Perhaps it could even be used in forward or reverse to help control temperature as well (small addition to local temperature as controlled)?
(c) In reverse as a voltage reference.

When used in reverse as a second voltage reference one could
(d) Get a negative reference voltage to match the positive which could be useful for miscellaneous purposes.
(e) Ger a negative reference voltage to match the positive one and so the back to back series voltage could be measured like a null measurement to look for differential drift of the two diodes.  This could be useful for stability tracking of the voltage outputs.
(f) The pair of voltages could be assessed independently for noise and drift so one could get two measurements from one unit. 
(g) It could be determined how good the matching of characteristics are between the two diodes which may or may not be monolithic adjacent pads on the same wafer or which could be two different die which are likely from the same wafer and may or may not generally be from adjacent sites. In any case knowing the matching of the two devices that ought to be as similar as possible could indicate the stability of performance of either / both over time and use.
(h) If one device is noisy the other one could be used as a primary reference output.   
(i) and of course be bringing out the signal forward / reverse tempco measurement can be made for use in analysis & R&D of subsequent uses / circuits whether for purposes of reference or temperature controller.

If for practical circuit uses there is to be any use cases of using the dual diodes to make bipolar references then it should be characterized as such with a constant current flowing through both diodes to see how that use case could perform.
 
What about using the second zener to reduce noise instead?  Feeding it to a separate opamp and then combining reduces the noise by a factor of 1/sqrt(2). While not much this would give an easy improvement for the price of an extra opamp.

Using it just for temp sensing seems a sacrilege.. that could be easily done by gluing a thermistor on top of it.

-BK
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #135 on: November 07, 2016, 12:25:40 AM »
Has anyone managed to find a more comprehensive datasheet for these parts? I successfully downloaded the one that zlymex linked in his first post (the 2 page Shen Xin one) but didn't have any success downloading the ones he linked later.

I've attached one pdf datasheet that I found (SJ brand), it appears to include lots of environmental test requirents but is mostly incomprehensible to me. I guess one from the 17th Radio Factory itself would be the holy grail. It, or a translation, might help answer some of the questions that are coming up.

Chris

(Edit: typo)
« Last Edit: November 07, 2016, 12:46:50 AM by Gyro »
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Offline Kleinstein

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #136 on: November 07, 2016, 12:49:57 AM »
It is a good question whether the two zeners are just normal zener diodes (like 6.2 V reference diodes) or they are supposed to used as a pair in series as a 7 V reference more like the 1N829 or similar.

There are both ways to get a low TC reference diode at the right current: either just a suitable zener diode at about 5-6 V or a compensated version with a zener and normal diode in series like in the 1N829, usually in the 7 V range or higher.

As the voltage is only 6.2 V, I would expect a relatively normal zener. We don't really know much about the internal details - at least they seem to be much lower noise than normal zener diodes. So there is like a more or less secret detail that makes these diodes so special.

Normally the TC of a silicon diode in forward direction is not depending on details of the diode: usually one has a linear temperature dependence that extrapolates to 1.2 V at 0 K. Higher current gives a higher voltage and thus lower TC. Thus a diode with 600 mV forward drop at 300 K will have a -2 mV/K slope.

As the diodes are connected common anode, there is no way to use them in series as a 12.4 V ref. One might be able to use the second diode as a backup to check for drift - but this would likely be better with a completely separate one.

With no detailed DS one might want to do a few measurements, e.g. voltage as a function of current an temperature to get TC and differential resistance. To really get the best working conditions one might need these data for the individual units anyway.
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #137 on: November 07, 2016, 01:26:34 AM »
It is a good question whether the two zeners are just normal zener diodes (like 6.2 V reference diodes) or they are supposed to used as a pair in series as a 7 V reference more like the 1N829 or similar.

There are both ways to get a low TC reference diode at the right current: either just a suitable zener diode at about 5-6 V or a compensated version with a zener and normal diode in series like in the 1N829, usually in the 7 V range or higher.

As the voltage is only 6.2 V, I would expect a relatively normal zener. We don't really know much about the internal details - at least they seem to be much lower noise than normal zener diodes. So there is like a more or less secret detail that makes these diodes so special.

Hello,

I think you have never had a 1N829 in hand.
The 1N829 has around 6.4V. (one of the usual voltages of temperature compensated zeners).
It is a normal diode 0.7V (-2mV/K) and a Zener (around 5.7 so +2mV/K) in series.
If you measure the 1N829 zener in "forward direction" you will find the breakdown voltage of the normal diode.
(which is beyond 15 V).

with best regards

Andreas
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #138 on: November 07, 2016, 02:47:26 AM »
I happened to measure a few 1N827 to 829 a few days ago, they were in the 6.2-6.3V range. The highest was a very old ex Solartron 1N829A which came out at 6.37V iirc, all at 7.5mA. It's only LM399, LTZ etc that are in the 6.95V range.

If that is in the same range as the 2DW233 then it is either a zener+series diode or a higher voltage zener with unsusual TC characteristics.  If it is a zener + diode combo then that will exclude using the second one as a sense diode... 1N82x don't conduct backwards (forwards in the conventional sense), the series diode is reverse biased.  :-\

This is the sort of thing a more comprehensive (and comprehensible?) datasheet would tell us.
« Last Edit: November 07, 2016, 02:57:40 AM by Gyro »
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Online Andreas

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #139 on: November 07, 2016, 03:01:42 AM »
Hello,

in the 1N82x series there are also some back to back zeners available (1N824) (but without center tap)
in this case both directions will have the 5.9-6.5 V zener voltage.
http://www.microsemi.com/document-portal/doc_download/10940-sa6-3-pdf

The trick of having a forward biased diode and a zener diode is that there will be a "zero TC" current
where the diode and zener TC are compensated to near zero over a small temperature range.

with best regards

Andreas


 

Offline evb149

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #140 on: November 07, 2016, 04:19:06 AM »
Someone claimed that the 1N823 also has superior noise characteristics, though I don't have any to test and there are not specific details.
http://www.diyaudio.com/forums/parts/35821-some-noise-measurements-leds-zener-diodes-12.html#post960894
"By chance I found that the noise of an 1N823 (6.2V temperature compensated) is dramatically less than that of ordinary zeners, even when you need more than one for getting the required voltage."

If I recall correctly I think I saw that the noise of a zener is related to its area and current density which makes sense if a larger area is like putting more devices in parallel.  If that is the case then perhaps part of the lower noise of such devices could simply be that they are larger area devices?

Hello,

in the 1N82x series there are also some back to back zeners available (1N824) (but without center tap)
in this case both directions will have the 5.9-6.5 V zener voltage.
http://www.microsemi.com/document-portal/doc_download/10940-sa6-3-pdf

The trick of having a forward biased diode and a zener diode is that there will be a "zero TC" current
where the diode and zener TC are compensated to near zero over a small temperature range.

with best regards

Andreas
 

Online Andreas

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #141 on: November 07, 2016, 05:22:53 AM »
Hello,

my measurements on several 1N829A (which are only specified for lesser T.C. (at 7.5mA) than 1N823) range from 2uVpp to 22uVpp 1/f noise (0.1 .. 10Hz).
This depends much on manufacturer.
I do not know if the quality nowadays is still the same...

The lesser noise (compared to higher voltage zeners in the link) might result from lower dynamic resistance.
Which is below 10 Ohms for around 6V compared to around 100 Ohms or more for higher voltage zeners.

With best regards

Andreas

 
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Offline evb149

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #142 on: November 07, 2016, 04:10:05 PM »
Hello, thank you very much, that is interesting and good information about your findings with these parts.

Hello,

my measurements on several 1N829A (which are only specified for lesser T.C. (at 7.5mA) than 1N823) range from 2uVpp to 22uVpp 1/f noise (0.1 .. 10Hz).
This depends much on manufacturer.
I do not know if the quality nowadays is still the same...

The lesser noise (compared to higher voltage zeners in the link) might result from lower dynamic resistance.
Which is below 10 Ohms for around 6V compared to around 100 Ohms or more for higher voltage zeners.

With best regards

Andreas
 

Offline technix

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #143 on: November 07, 2016, 04:31:12 PM »
I have talked with factory that originally made those 2DW233's, Shanghai No. 17 Radio Factory, and I can order them for you fresh from the factory if you want to.
 
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Offline zlymex

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #144 on: November 07, 2016, 04:44:35 PM »

If I recall correctly I think I saw that the noise of a zener is related to its area and current density which makes sense if a larger area is like putting more devices in parallel.  If that is the case then perhaps part of the lower noise of such devices could simply be that they are larger area devices?

That is not the case. If we parallel four identical devices and run the same current, the noise would be the same.
Parallel four devices and the noise is halved, this only happens if the total current is quadrupled. but this is equivalent to running the larger current on a single device.
The advantage of large area is the ability to run at larger current.
"2DW232 has much better noise than LTZ1000", this is compared at the same zener current.
 
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Offline 2N3055

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #145 on: November 07, 2016, 06:36:16 PM »
You can consider that large crystal is equivalent of many small crystals connected in parallel. All stochastic noise related events combine same as they would from dozens of separate parallel connected diodes..
Of course,  if  you run it as same current density as with separate diodes...
 
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Offline evb149

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #146 on: November 08, 2016, 12:57:49 PM »
Thank you very much, technix!

What information did you receive about prices for various quantity ranges?

I would be interested to order some, maybe others here will also be so.

I have talked with factory that originally made those 2DW233's, Shanghai No. 17 Radio Factory, and I can order them for you fresh from the factory if you want to.
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #147 on: November 08, 2016, 01:01:21 PM »
Thank you very much, zlymex, and 2N3055, your explanations are logical.
 

That is not the case. If we parallel four identical devices and run the same current, the noise would be the same.
Parallel four devices and the noise is halved, this only happens if the total current is quadrupled. but this is equivalent to running the larger current on a single device.
The advantage of large area is the ability to run at larger current.
"2DW232 has much better noise than LTZ1000", this is compared at the same zener current.

You can consider that large crystal is equivalent of many small crystals connected in parallel. All stochastic noise related events combine same as they would from dozens of separate parallel connected diodes..
Of course,  if  you run it as same current density as with separate diodes...
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #148 on: November 08, 2016, 03:07:46 PM »
Thank you very much, technix!

What information did you receive about prices for various quantity ranges?

I would be interested to order some, maybe others here will also be so.

I have talked with factory that originally made those 2DW233's, Shanghai No. 17 Radio Factory, and I can order them for you fresh from the factory if you want to.

They gave me a solid 75 US cents each regardless of amount, and for order more than 50 (a whole pack) they will pay for the shipping from their factory to my home. When I send it on the shipping cost would be $5 for less than 2kg.
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #149 on: November 08, 2016, 03:33:26 PM »
Here is the test circuit I am going to use when selecting the 2DW233 for you.

ADC is the built-in 10-bit unit inside ATmega328P, while DAC is TLC5615 (8-bit) referenced from ADR03B. The microcontroller will perform a search to find the best approximate of the zero TC point in the range of 0mA to about 50mA.
« Last Edit: November 08, 2016, 04:59:11 PM by technix »
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #150 on: November 08, 2016, 10:33:32 PM »
Here is the test circuit I am going to use when selecting the 2DW233 for you.

ADC is the built-in 10-bit unit inside ATmega328P, while DAC is TLC5615 (8-bit) referenced from ADR03B. The microcontroller will perform a search to find the best approximate of the zero TC point in the range of 0mA to about 50mA.
2DW232 is very sensitive to the supply current, therefore I suspect the short term stabllity of the current mirror unless they are paired and thermally bonded.

Theoritically, to test the zero T.C. points(there are many for one device), there is the need both for varying the current and the temperature.
Practically, a step current can be used, then monitor the voltage variation direction to determin whether the current is Ok.
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #151 on: November 08, 2016, 11:40:45 PM »
Here is the test circuit I am going to use when selecting the 2DW233 for you.

ADC is the built-in 10-bit unit inside ATmega328P, while DAC is TLC5615 (8-bit) referenced from ADR03B. The microcontroller will perform a search to find the best approximate of the zero TC point in the range of 0mA to about 50mA.
2DW232 is very sensitive to the supply current, therefore I suspect the short term stabllity of the current mirror unless they are paired and thermally bonded.

Theoritically, to test the zero T.C. points(there are many for one device), there is the need both for varying the current and the temperature.
Practically, a step current can be used, then monitor the voltage variation direction to determin whether the current is Ok.

In practise I am using the BCV62 for the current mirror - the two PNPs are built on the same piece of silicon and are factory matched. I have already breadboarded the setup and tests on my stock of 1N4728 and 1N4734 are showing the correct behavior. I can scan through 0 to 25mA (I ended up using a 199.7 ohm resistor instead of 100 ohm one as the current sense resistor) at about 0.1mA step and measure the voltage with this automated jig.

I will implement a faster search algorithm that can find the optimal current on the MCU and a component insert sense feature, so when the parts arrive I can bulk test them very rapidly.
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #152 on: November 09, 2016, 12:02:29 AM »
To measure the voltage change one should use a way more capable ADC / DMM or maybe measure only difference towards a fixed voltage close by. For a 10 ppm/K TC and 10 K Temperature step, one has only bout a .6 mV change. So something like a 14 Bit resolution would be the minimum - better more.

Changing the current can also change the internal temperature - though at least the temperature increase should be about proportional to current and reproducible.
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #153 on: November 09, 2016, 01:29:52 AM »
To measure the voltage change one should use a way more capable ADC / DMM or maybe measure only difference towards a fixed voltage close by. For a 10 ppm/K TC and 10 K Temperature step, one has only bout a .6 mV change. So something like a 14 Bit resolution would be the minimum - better more.

Changing the current can also change the internal temperature - though at least the temperature increase should be about proportional to current and reproducible.

I was searching for the Iz with maximum Vz. Maybe I do need a better ADC though, but otherwise my rig is fully automated and can detect the insert of DUT and can search for that Iz point.
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #154 on: November 09, 2016, 03:36:12 AM »
To measure the voltage change one should use a way more capable ADC / DMM or maybe measure only difference towards a fixed voltage close by. For a 10 ppm/K TC and 10 K Temperature step, one has only bout a .6 mV change. So something like a 14 Bit resolution would be the minimum - better more.

Changing the current can also change the internal temperature - though at least the temperature increase should be about proportional to current and reproducible.

I was searching for the Iz with maximum Vz. Maybe I do need a better ADC though, but otherwise my rig is fully automated and can detect the insert of DUT and can search for that Iz point.

If you measure differentially against a stable voltage source that's close to the expected zener voltage and then add a bit of gain you'll get much better sensitivity. I'm concerned that you've looking for effects that are on a very close order to the LSB step of the ATMega's ADC. You could derive your stable voltage from the same reference you use for the ADC. You might even gain a tiny advantage from this giving you a ratiometric measurement vs your voltage reference.

I don't exactly know what the expected spread of voltage with individual part variations and temperature is, but if we say for argument sake it is +/-300mV and your original measurement range was 0-10V that would give a resolution improvement of 17 times for the cost of an op amp and a few resistors. That's an LSB of 585 uV versus your original LSB of 9.76 mV. I think you need this and at least a couple more bits on the ADC. The latter would give you a ~125 uV LSB.
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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #155 on: November 09, 2016, 03:59:34 AM »
One is not looking for the current with maximum Vz. The Voltage should go up with current over the full range - unless the temperature rise is to much. This point is not what one is looking for. The interesting point is the current at which the voltage is not temperature dependent in linear approximation for the right temperature range, e.g. with 30 C environment or a higher temperature like 50-60C when used with temperature stabilization.

So one would really need to resolve small changes (like 10 µV) in the voltage. So the test rig would be a little more complicated. More like using a commercial DMM (or high resolution ADC) to measure the voltage. The µC internal ADC is more like good enough to read the temperature from the other diode.
If you really want to go with the µC internal (10 Bit) ADC one might be able to only measure the difference to a second reference and use the ADC only for a maybe +-50-100 mV.

So the procedure could be:
0) at RT measure the forward voltage of the second diode, to calibrate it as a thermometer.
1) set test current for a first try
2) Adjust the second ref. voltage so that the difference to the DUT is small (e.g. < 50  mV)
3) Put a relatively high current (e.g. 10-20 mA) through the second diode in the chip, to cause some heat up
4) Change the current to the second diode to a small one in forward direction to use it for temperature measurement
5) do a fast measurement of voltage difference and temperature during cooling (e.g. 5-30 seconds). Temperature measurement is not that critical - decay curve should be similar for the devices.
It more to get the average temperature and an estimate for the order of magnitude.
6) calculate / estimate TC for the given test current and temperature range
7) adjust the current to get lower TC   (e.g. interpolate / extrapolate form older points and maybe typical curve).
8) Repeat if needed (TC to large).

For just a few parts one could do this also by hand - reading the drop on a DMM.
If you really need to automate, I would look for a better external ADC (e.g. 16-24 Bits).
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #156 on: November 09, 2016, 04:49:04 AM »
Or just use a SMU......
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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #157 on: November 09, 2016, 05:20:39 AM »
So how do you guys think about this idea:

On the board I have an ADR03B that is used by the constant current generator. I can wire up the resistive divider so the divided buffered output from 2DW233 is also close to the output voltage of ADR03B. Then I can use the built-in differential PGA of the ATmega to measure the ratiometric difference of 2DW233 and ADR03B with a relatively high gain.

Rinse and repeat in a fridge or on top of a boiling kettle.
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #158 on: November 09, 2016, 05:38:40 AM »
So how do you guys think about this idea:

On the board I have an ADR03B that is used by the constant current generator. I can wire up the resistive divider so the divided buffered output from 2DW233 is also close to the output voltage of ADR03B. Then I can use the built-in differential PGA of the ATmega to measure the ratiometric difference of 2DW233 and ADR03B with a relatively high gain.

Rinse and repeat in a fridge or on top of a boiling kettle.

For low noise high stability applications mostly the performance in a reasonably narrow temperature range (say, 20C-50C) is important. I would use a temperature cycling device made out of a small Peltier cooler and a local heater for the zener, so the temperature swing can be arranged by just switching the heater on/off (as Peltier modules do not like switching polarity quickly) and the optimum current will be found for the smallest voltage change from cold to warm and back.

Cheers

Alex
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #159 on: November 09, 2016, 05:47:30 AM »
I don't know what kind of power element should be used to heat it up. Scanning the entire current range takes about 2.5 seconds using my fully automated design but things can be cooled down quite a bit by then. If I can digitally control the temperature even only with 8 bit resolution I can still characterize those diodes fairly well and can fully automate it (so you just plug in the component and wait until a full report is spit out from the AVR.)
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #160 on: November 09, 2016, 06:01:33 AM »
The amplifier inside the AVRs is not really good, but in principle it could work with the difference.
With a gain of 200 the signal range would be somewhere in the 12 mV range and resolution at about 10 µV. With a divider to about half to third - this is 20-30 µV resolution for the reference.

The reference (ADR03) might need some noise filtering. Due to noise (e.g. amplifier) it may also take some averaging to get good enough data.
The divider needs individual adjustment (but still really stable) for each diode to bring it in the range. It might limit the current range used in one go.

The interesting temperatures would be more like normal room temperature or a little up, maybe up to 50 C environment. No real need for data below room temperature. Getting data on TC versus current at near room temperature (only self heating, maybe increased from the second diode) is already an important part. The optimum current should not be that much temperature dependent.

If you want a real characterization you would need a better ADC, to get the full resolution and thus also get direct data, so no adjustable divider. This is something a SMU is made for - if you have one.
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #161 on: November 09, 2016, 06:18:17 AM »
The amplifier inside the AVRs is not really good, but in principle it could work with the difference.
With a gain of 200 the signal range would be somewhere in the 12 mV range and resolution at about 10 µV. With a divider to about half to third - this is 20-30 µV resolution for the reference.

The reference (ADR03) might need some noise filtering. Due to noise (e.g. amplifier) it may also take some averaging to get good enough data.
The divider needs individual adjustment (but still really stable) for each diode to bring it in the range. It might limit the current range used in one go.

The interesting temperatures would be more like normal room temperature or a little up, maybe up to 50 C environment. No real need for data below room temperature. Getting data on TC versus current at near room temperature (only self heating, maybe increased from the second diode) is already an important part. The optimum current should not be that much temperature dependent.

If you want a real characterization you would need a better ADC, to get the full resolution and thus also get direct data, so no adjustable divider. This is something a SMU is made for - if you have one.
I don't have a SMU but I do have MCP3911, a dual channel 24-bit ADC with internal 1.7V reference and differential inputs. Maybe I can use that?

And still how do I control the temperature of the diodes? If I heat up the chip using one of the two diodes, will PWM work?
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #162 on: November 09, 2016, 07:02:39 AM »
Using the MCP3911 could work to build a higher resolution measurement system. Only the low voltage range (like +-600 mV) might be a little inconvenient and need some care against thermal EMF. So it is possible, but not very easy and more like a separate project first.

The resolution is good enough to eliminate the subtraction. And stability should be good enough to measure Vz versus current at different temperatures instead of changes in Vz on fast modulated temperature. Though you still have the option to measure fast.  Later you can than sort the data towards  voltage versus temperature for the different current settings.

For heating the chip PWM on the second diode could work. The downside is that you can only measure well when the heating current is off, as they share a common pin. So one would have a heating phase and one for measuring the zener ref. and the other diode as a temperature sensor with a much lower current (e.g 100 µA) in the other direction. This could work for more moderate temperatures (e.g. 10-40 K temperature rise). The internal heater is fast, but limited power. PWM on the second diode could also introduce thermal gradients and thus mechanical stress, so this would not be the most accurate way.

For higher temperature or very accurate data an external heater would be needed. The external heater might be controlled by PWM. One might not need to have a control loop, but could do the measurements during slow heat-up and cool-down. The second diode could be used as a temperature sensor.
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #163 on: November 11, 2016, 01:43:24 PM »
I mounted one of the 2DW232 parts on to a banana plug, plugged it into a KE2461 forcing 5mA. I am monitoring voltage with a DMM7510.

The voltage is 6.02xxxx and wanders about 600uV p-p, 166 uV standard deviation.

I traded some PMs with chuckb. He tried forcing current into a 2DW23X part with a calibrator and saw the voltage wandering as well.

My opinion is that the instruments that can force current are not ppm stable and cannot be relied upon to maintain stable enough current for a zener reference device.

Any other opinions?
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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #164 on: November 11, 2016, 02:38:53 PM »
What about making a precision current source? You have precision resistors, right.
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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #165 on: November 11, 2016, 04:11:39 PM »
I mounted one of the 2DW232 parts on to a banana plug, plugged it into a KE2461 forcing 5mA. I am monitoring voltage with a DMM7510.

The voltage is 6.02xxxx and wanders about 600uV p-p, 166 uV standard deviation.

I traded some PMs with chuckb. He tried forcing current into a 2DW23X part with a calibrator and saw the voltage wandering as well.

My opinion is that the instruments that can force current are not ppm stable and cannot be relied upon to maintain stable enough current for a zener reference device.

Any other opinions?

You need a more stable source to compare it against, for example LM399.
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #166 on: November 11, 2016, 08:38:22 PM »
I mounted one of the 2DW232 parts on to a banana plug, plugged it into a KE2461 forcing 5mA. I am monitoring voltage with a DMM7510.

The voltage is 6.02xxxx and wanders about 600uV p-p, 166 uV standard deviation.

I traded some PMs with chuckb. He tried forcing current into a 2DW23X part with a calibrator and saw the voltage wandering as well.

My opinion is that the instruments that can force current are not ppm stable and cannot be relied upon to maintain stable enough current for a zener reference device.

Any other opinions?

You need a more stable source to compare it against, for example LM399.

Have you watched Dave's teardown of the DMM7510? the DMM7510 has an ovenized LTFLU as its reference. This same ovenized LTFLU is what provides the Fluke 5700A DC volts reference .

The DMM7510 can measure the 3ppm daily drift of my Fluke 731B (two of them) in my lab/office.The 731B drifts 1 ppm for every 2 or 3 degrees F.

The LM399 is what is inside my calibrated KE2000 and it is a very stable and it agrees with my DMM7510. The DMM7510 has 10X resolution measuring the daily drift of the 731B compared to the KE2000.
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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #167 on: November 11, 2016, 08:41:04 PM »
What about making a precision current source? You have precision resistors, right.

I do have some precision resistors. They would probably require tempco tweaking to make a better current source than what is in the KE2461. Its a good idea. That will have to go on the long list of future projects.
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Offline Kleinstein

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #168 on: November 11, 2016, 09:20:53 PM »
If would also suspect the current source, though this should not be that bad. Also EMI could be a problem, when using an external unit.
There is also a chance that there is quite some temperature effect, as the TC is low only for a suitable current and this current can be vary quite a lot from device to device. Having one with 6.0x V suggest this could be one of the more extreme ones. So if possible I would also monitor the temperature via the second diode.

The normal test circuit would be similar to the one right at the beginning of the thread.
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #169 on: November 11, 2016, 10:29:56 PM »
If would also suspect the current source, though this should not be that bad. Also EMI could be a problem, when using an external unit.
There is also a chance that there is quite some temperature effect, as the TC is low only for a suitable current and this current can be vary quite a lot from device to device. Having one with 6.0x V suggest this could be one of the more extreme ones. So if possible I would also monitor the temperature via the second diode.

The normal test circuit would be similar to the one right at the beginning of the thread.

I think that the SMU is not the largest contributor to the 100+ uV wander of the zener.

I just changed the forced current to 10mA and the average wander is now 6 uV instead of 100+ uV at 5mA.

It looks like an automated measurement will be required to characterize all 10 pcs of the 2DW232 that I will be using.

The 2DW232 mounted on the banana plug is wrapped in 3 tissues tied with a twist tie.

Another thing to mention here is that it takes 30+ minutes for the 2DW232 to stabilize. In open air, it never stabilizes.
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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #170 on: November 11, 2016, 10:54:29 PM »
I can test with my SMUs (K2400 and HP 4142) and try automate tempco finding, once I get few of these little wonders too.
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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #171 on: November 11, 2016, 11:05:55 PM »
If would also suspect the current source, though this should not be that bad. Also EMI could be a problem, when using an external unit.
There is also a chance that there is quite some temperature effect, as the TC is low only for a suitable current and this current can be vary quite a lot from device to device. Having one with 6.0x V suggest this could be one of the more extreme ones. So if possible I would also monitor the temperature via the second diode.

The normal test circuit would be similar to the one right at the beginning of the thread.

I think that the SMU is not the largest contributor to the 100+ uV wander of the zener.

I just changed the forced current to 10mA and the average wander is now 6 uV instead of 100+ uV at 5mA.

It looks like an automated measurement will be required to characterize all 10 pcs of the 2DW232 that I will be using.

The 2DW232 mounted on the banana plug is wrapped in 3 tissues tied with a twist tie.

Another thing to mention here is that it takes 30+ minutes for the 2DW232 to stabilize. In open air, it never stabilizes.

To find the optimal current for minimum tempco you have to do a temperature change, for example heating the zener with a power resistor, letting it to cool down (with a several seconds repetition time), and adjust the current for a minimal change in voltage. It is also would be interesting to see if the minimum tempco would be for one zener only or for a zener in series with the second half working as a diode (which I suspect might be the case).

Cheers

Alex
« Last Edit: November 11, 2016, 11:10:19 PM by Alex Nikitin »
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #172 on: November 11, 2016, 11:18:15 PM »
For manual finding the optimum current, one could look an the stabilization curve (the first 10-20 seconds or so) after turning the current on. For too low a current, the voltage should drift down on settling and for to high a current the settling should be upwards.
Of cause one can do the same with the SMU and PC as well.

As heater one could use the second zener as well, so the observed voltage will stay about the same and one could use an AC coupled amplifier to watch small changes.

The much better performance at 10 mA suggests that the wandering / drift was due to thermal effects and 10 mA being much closer to the point of zero TC. Only 6 µV suggests this is already rather close - e.g. a TC of a few ppm / K at most. Final performance can also depend slightly on the resistor to set the current and the environment temperature range.
 

Offline VintageNut

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #173 on: November 11, 2016, 11:46:12 PM »
For manual finding the optimum current, one could look an the stabilization curve (the first 10-20 seconds or so) after turning the current on. For too low a current, the voltage should drift down on settling and for to high a current the settling should be upwards.
Of cause one can do the same with the SMU and PC as well.

As heater one could use the second zener as well, so the observed voltage will stay about the same and one could use an AC coupled amplifier to watch small changes.

The much better performance at 10 mA suggests that the wandering / drift was due to thermal effects and 10 mA being much closer to the point of zero TC. Only 6 µV suggests this is already rather close - e.g. a TC of a few ppm / K at most. Final performance can also depend slightly on the resistor to set the current and the environment temperature range.

Short answer: the voltage never settles upwards.

The datasheet that Zlymex posted has max power at 200mW and current of 30mA.

I have tested one sample at 5mA, 10mA, 15mA, 20mA, 25mA and 30mA. The device is wrapped in three layers of tissue to kill any air current.

The voltage always decreases for many minutes until a stable voltage is reached.

The particular device in-hand operates at 6.19xxxx volts at 30 mA. I will let this device run at 30mA until it settles and report +/- deviation.
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Online Alex Nikitin

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #174 on: November 12, 2016, 12:01:11 AM »
Short answer: the voltage never settles upwards.

And what happens if you connect both sides (one as a zener, one as a diode in series with zener)?

Cheers

Alex
 

Offline VintageNut

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #175 on: November 12, 2016, 12:37:41 AM »
Short answer: the voltage never settles upwards.

And what happens if you connect both sides (one as a zener, one as a diode in series with zener)?

Cheers

Alex

I am not sure what you are asking to try. Maybe draw it out by hand and post the drawing(s)?
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Offline VintageNut

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #176 on: November 12, 2016, 12:43:31 AM »
Here is a screen capture of the statistics of the DMM7510 measuring voltage .

Keep in mind that the voltage measure cables are unshielded  24" long each. I will use shielded BNC cable eventually when I have a 2DW232 on a pcb in an enclosure.


RMS noise (standard deviation) is less than 1/2 uV.


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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #177 on: November 12, 2016, 01:12:33 AM »
Short answer: the voltage never settles upwards.

And what happens if you connect both sides (one as a zener, one as a diode in series with zener)?

Cheers

Alex

I am not sure what you are asking to try. Maybe draw it out by hand and post the drawing(s)?

Like that:

Cheers

Alex
 

Offline VintageNut

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #178 on: November 12, 2016, 02:00:48 AM »
Short answer: the voltage never settles upwards.

And what happens if you connect both sides (one as a zener, one as a diode in series with zener)?

Cheers

Alex

I am not sure what you are asking to try. Maybe draw it out by hand and post the drawing(s)?

Like that:

Cheers

Alex

I believe that is how it is connected and is how it is intended to be used. Pin 1 is the red dot which is the output. Pin 2 is grounded. Pin 3 is the case is ignored.
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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #179 on: November 12, 2016, 02:07:11 AM »
I believe that is how it is connected and is how it is intended to be used. Pin 1 is the red dot which is the output. Pin 2 is grounded. Pin 3 is the case is ignored.

OK, thanks, that was my understanding as well, however from the discussion in this thread it was not quite clear.

Cheers

Alex
 

Offline VintageNut

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #180 on: November 12, 2016, 03:58:29 AM »
For manual finding the optimum current, one could look an the stabilization curve (the first 10-20 seconds or so) after turning the current on. For too low a current, the voltage should drift down on settling and for to high a current the settling should be upwards.
Of cause one can do the same with the SMU and PC as well.

As heater one could use the second zener as well, so the observed voltage will stay about the same and one could use an AC coupled amplifier to watch small changes.

The much better performance at 10 mA suggests that the wandering / drift was due to thermal effects and 10 mA being much closer to the point of zero TC. Only 6 µV suggests this is already rather close - e.g. a TC of a few ppm / K at most. Final performance can also depend slightly on the resistor to set the current and the environment temperature range.

It appears to be the opposite of your hypothesis.
For too-high current, the voltage drifts down. For too-low current, the voltage drifts up.

Now that that is sorted out, the zero T-C current for this device is between 7mA and 8mA in open air.  Covered in tissues the zero T-C current is between 6mA and 7mA.

That's better!
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Offline Kleinstein

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #181 on: November 12, 2016, 04:44:25 AM »
An 6-8 mA current for zero TC sounds very good. However the optimum current seems to be quite temperature dependent if it already changes so much from open to air and covered.

It is interesting to see an negative TC and thus falling voltage at high current. The normal zener refs like 1N829 are the other way around with a negative TC at low currents and a positive at high currents.

It might be interesting to do full characterization with 1 or 2 samples, as this units seem to be different from the more normal western zeners and the DS does not give much information. Is the diode in forward direction reasonably normal and working as a temperature sensor ?
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #182 on: November 12, 2016, 05:06:48 AM »
I will mount a second device and take the same tests for currents causing rising and falling current. And I will have a try at measuring a single diode.
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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #183 on: November 12, 2016, 05:27:47 AM »
An 6-8 mA current for zero TC sounds very good. However the optimum current seems to be quite temperature dependent if it already changes so much from open to air and covered.

It is interesting to see an negative TC and thus falling voltage at high current. The normal zener refs like 1N829 are the other way around with a negative TC at low currents and a positive at high currents.

It might be interesting to do full characterization with 1 or 2 samples, as this units seem to be different from the more normal western zeners and the DS does not give much information. Is the diode in forward direction reasonably normal and working as a temperature sensor ?

A second mounted sample works exactly the same. High current causes voltage to fall. Low current causes voltage to rise.
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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #184 on: November 12, 2016, 10:47:11 AM »
I will mount a second device and take the same tests for currents causing rising and falling current. And I will have a try at measuring a single diode.

I mounted a device with the red dot at HI of the SMU. The device case is at LO of the SMU.

1mA of forced current creates 0.73 V. 1mA of reverse current creates -5V.

5mA creates  0.78V. -5mA creates -5.26V

I think that explains the device behavior.
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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #185 on: November 12, 2016, 12:55:24 PM »

1mA of forced current creates 0.73 V. 1mA of reverse current creates -5V.

5mA creates  0.78V. -5mA creates -5.26V

I think that explains the device behavior.

 Seems to me that you're measuring a combination of temperature coefficient and dynamic resistance there, and the two measurements are not even the same difference in temperature.  I don't know how to draw any conclusions from it.
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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #186 on: November 12, 2016, 01:18:34 PM »

1mA of forced current creates 0.73 V. 1mA of reverse current creates -5V.

5mA creates  0.78V. -5mA creates -5.26V

I think that explains the device behavior.

 Seems to me that you're measuring a combination of temperature coefficient and dynamic resistance there, and the two measurements are not even the same difference in temperature.  I don't know how to draw any conclusions from it.

The observation is that there are two devices; a 5V zener in series with a 0.7v diode. Nothing more complicated than that.
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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #187 on: November 12, 2016, 07:22:39 PM »
The observation is that there are two devices; a 5V zener in series with a 0.7v diode. Nothing more complicated than that.

Just for clarity, are you concluding that using the circuit of Alex in http://www.eevblog.com/forum/metrology/ultra-low-noise-reference-2dw232-2dw233-2dw23x/msg1068444/#msg1068444 or are you grounding the open midpoint and are you applying  a positive voltage > 7V, via a resistor, to the kathode of D2?

I would think that D2 is a diode, because it is as a reversed zener  in the first case. Or are we saying the same?
« Last Edit: November 12, 2016, 08:16:46 PM by SvanGool »
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Offline Kleinstein

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #188 on: November 12, 2016, 08:05:01 PM »
So a low TC can be obtained with both diodes in series, as an 5.4 V zener with posistive TC  and one working as a normal diode with negative TC. At some current (about 5-10 mA) the TCs will compensate, since the TC depends on the current. For a normal diode the TC gets smaller (less negative) with more current. For this zener it seems the TC is also getting smaller (a little faster than that of the diode) at high current as the overall TC seems to turn negative on high currents.

Having the two diodes in series makes it possible to use the normal diode as a temperature sensor - for compensation of residual temperature dependence (not just linear) or a regulated temperature. With the diode as a sensor one might be able to get quantitative values for the TC at maybe 5 and 10 mA.

The rather good stability even at 10 mA for a device with compensating current near 7-8 mA suggests that even with not so perfect current the TC is quite low.

o far the reference looks very good - 2 more points to check:
1) One point is hysteresis: So is the voltage the same starting from cold or a higher temperature.
    For a test one could do a sequence like: off - 7.5 mA (optimum current) - 25 mA (to heat the device)  and than 7.5 mA again.

2) The last big question is long time stability. Here the SMU might not be good enough as a current source and this would be more like testing ready made reference units with case and possibly temperature control.
 

Offline VintageNut

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #189 on: November 13, 2016, 11:08:00 AM »
So a low TC can be obtained with both diodes in series, as an 5.4 V zener with posistive TC  and one working as a normal diode with negative TC. At some current (about 5-10 mA) the TCs will compensate, since the TC depends on the current. For a normal diode the TC gets smaller (less negative) with more current. For this zener it seems the TC is also getting smaller (a little faster than that of the diode) at high current as the overall TC seems to turn negative on high currents.

Having the two diodes in series makes it possible to use the normal diode as a temperature sensor - for compensation of residual temperature dependence (not just linear) or a regulated temperature. With the diode as a sensor one might be able to get quantitative values for the TC at maybe 5 and 10 mA.

The rather good stability even at 10 mA for a device with compensating current near 7-8 mA suggests that even with not so perfect current the TC is quite low.

o far the reference looks very good - 2 more points to check:
1) One point is hysteresis: So is the voltage the same starting from cold or a higher temperature.
    For a test one could do a sequence like: off - 7.5 mA (optimum current) - 25 mA (to heat the device)  and than 7.5 mA again.

2) The last big question is long time stability. Here the SMU might not be good enough as a current source and this would be more like testing ready made reference units with case and possibly temperature control.

Forcing current with a SMU, the voltage is never stable in the bottom 3 or 4 digits. There is no way to measure hysteresis unless a very stable circuit is built and placed in an enclosure.

My opinion is that a stable circuit will require the same heroic effort that is built into a Fluke 731B. Selected and matched tempco resistors. Lots of places for mistakes to show up.

Then the reference diodes have to be aged and characterized and only the best one is good enough.

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Offline evb149

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #190 on: November 13, 2016, 11:38:36 AM »
I just had a "quick and dirty" thought about sending a fairly low noise / stable current through these somewhat easily.
If the SMUs and PSUs tend to be too noisy / erratic when sourcing current into them, maybe something simple like a "12V" vechicle battery through a series resistor would be more stable and low noise at least over time spans of minutes at a time at this low output current level.  I suppose a laptop battery pack or something like that might also work if the voltage is high enough to give some decent headroom.

Of course air current / thermal variations would have to be kept to a minimum with something like Bob Pease's "nested cardboard boxes" trick and tissue or something.
 
 

Offline technix

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #191 on: November 13, 2016, 08:50:45 PM »
This week's order from factory is about to close. If you want to buy one of those please PM me.
 

Offline Kleinstein

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #192 on: November 13, 2016, 09:08:23 PM »
The differential resistance on the zeners should be reasonable low. So changes in the resistors are attenuated by a factor of about current setting resistor to zener resistance. This could be something in the range of 50-100 if one assumes 6 V to set the current. So the demands on the resistors are not that extreme.

For the first tests I would not assume the zeners to be as good as high end parts like LTZ1000 or LTFLU. We would be very happy it could come close to the LM399 / LM129H. So it is about resolving changes in the 10 ppm range. Some thermal shielding and soldering to a board is likely needed - alone from thermal EMF.

The measurements from VintageNut suggest he got quite good stability with the SMU as a current source. But it can depend on the individual units and environment. A dedicated reference circuit could work as well - the demands for the current setting resistors are not that high (e.g. even 100 ppm/K thick film might be good enough), at least for the hysteresis test.

Attached is a suggested simple test circuit. Paralleling R3 to R2 could be used to temporarily increase the current. The lower diode of the ref can be used to get a rough idea of the reference temperature.
 

Offline VintageNut

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #193 on: November 14, 2016, 12:59:02 AM »
Hello Kleinstein

Can you please give some analysis of how your circuit is better or different from the circuit used by zlymex on the first page of this thread?
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Offline Kleinstein

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #194 on: November 14, 2016, 03:14:52 AM »
The circuit I showed uses only 2 (instead of 3) resistors that need to be stable. Just to get a stable current for one ref. chip, even the second resistor does not really need to be a good one either.

The difference is also not that big - just replace D1/D3 with a resistor and you are back at the circuit from the first page.

For doing a transient / current step test, it might be an advantage that the current does not depend on the voltage of the ref chip under test, but on the other one. One can look at D2/D4 (e.g. 6.2 V) or at the sum of both references (12.4 V). If you want scaling to 10 V, it works slightly better (less sensitive to resistor drift) if you start from 12 V than starting from 6.2 V.
 

Offline edavid

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #195 on: November 18, 2016, 10:06:24 AM »
Here is the translated datasheet.

Thank you for preparing this translation, but I think the listed pinout is incorrect.  For the devices I received from VintageNut, pins 1 and 2 are anodes, and pin 3 is the common cathode.

Also, I measure a resistance of ~800K between the 2 anodes.  Does anyone know why that is?
 

Online Andreas

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #196 on: November 18, 2016, 04:52:48 PM »

Thank you for preparing this translation, but I think the listed pinout is incorrect.  For the devices I received from VintageNut, pins 1 and 2 are anodes, and pin 3 is the common cathode.

Hello,

The translation corresponds to the picture from the datasheet. (first page on the thread).
Do you really measure 5.6 instead of 0.7V on the ground referenced diode when using a pull-up resistor?

With best regards

Andreas
 

Offline edavid

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #197 on: November 18, 2016, 04:57:26 PM »
Thank you for preparing this translation, but I think the listed pinout is incorrect.  For the devices I received from VintageNut, pins 1 and 2 are anodes, and pin 3 is the common cathode.
The translation corresponds to the picture from the datasheet. (first page on the thread).
Yes, that is also incorrect (or doesn't match the parts I received).  Very odd.

Quote
Do you really measure 5.6 instead of 0.7V on the ground referenced diode when using a pull-up resistor?
Sorry, I don't understand this question.
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #198 on: November 18, 2016, 05:27:25 PM »
if you take the cirquit from Alex:

http://www.eevblog.com/forum/metrology/ultra-low-noise-reference-2dw232-2dw233-2dw23x/msg1068444/#msg1068444
e.g. with 15V supply and resistor = 1K

what voltage do you measure between Pin 3 (case of zener) and ground?

With best regards

Andreas
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #199 on: November 18, 2016, 07:51:06 PM »
I've measured (by a multimeter diode test only so far) one of the devices I've received and it is indeed a common cathode configuration, as shown on the attached diagram.

Cheers

Alex
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #200 on: November 18, 2016, 09:35:23 PM »
So its more difficult to measure the chip temperature since the forward diode is not referred to GND.

With best regards

Andreas
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #201 on: November 18, 2016, 09:52:06 PM »
So its more difficult to measure the chip temperature since the forward diode is not referred to GND.

With best regards

Andreas

It will be easy in a negative reference configuration though ;) . In a positive reference the diode can still be used easily for a temperature stabilization with an external heater.

Cheers

Alex
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #202 on: November 19, 2016, 12:45:05 AM »
I'm running a measurement on the first sample right now. The circuit is attached. R1 is actually a resistor decade set at 515 Ohm, that is a reasonably stable point. The zener is connected through an IC socket, the 10V source is my JVR reference, so it is quite stable, C1 is a Mylar film capacitor. Right now I'm using the 34465A. I might leave it running over the weekend with 3558A though.

Cheers

Alex

P.S. - first impressions are ... interesting. Very little random noise but the device is (relatively) sensitive to temperature variations and air movements. I suspect that it can only be useful with a good temperature stabilizing loop. With ~7.5mA and 6 Volts the dissipation is quite high and so is self-heating. As a result, any air movements produce noticeable voltage shifts (few ppm even with a good foam envelope around the device). The dynamic resistance at 7.5mA is about 13-14 Ohm. We'll see how it performs over the weekend.
« Last Edit: November 19, 2016, 02:16:05 AM by Alex Nikitin »
 

Offline edavid

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #203 on: November 19, 2016, 03:20:50 AM »
P.S. - first impressions are ... interesting. Very little random noise but the device is (relatively) sensitive to temperature variations and air movements. I suspect that it can only be useful with a good temperature stabilizing loop. With ~7.5mA and 6 Volts the dissipation is quite high and so is self-heating. As a result, any air movements produce noticeable voltage shifts (few ppm even with a good foam envelope around the device). The dynamic resistance at 7.5mA is about 13-14 Ohm. We'll see how it performs over the weekend.

Is your device a 2DW232 or 2DW233?  I know zlymex told us not to pay much attention to the nominal current, but...
 

Offline zlymex

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #204 on: November 19, 2016, 04:02:15 AM »
..... With ~7.5mA and 6 Volts the dissipation is quite high and so is self-heating. As a result, any air movements produce noticeable voltage shifts (few ppm even with a good foam envelope around the device). ......
The foam should be in touch with the case and legs, leaving as small gaps as possible. I just use tissues.
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #205 on: November 19, 2016, 04:56:33 AM »
P.S. - first impressions are ... interesting. Very little random noise but the device is (relatively) sensitive to temperature variations and air movements. I suspect that it can only be useful with a good temperature stabilizing loop. With ~7.5mA and 6 Volts the dissipation is quite high and so is self-heating. As a result, any air movements produce noticeable voltage shifts (few ppm even with a good foam envelope around the device). The dynamic resistance at 7.5mA is about 13-14 Ohm. We'll see how it performs over the weekend.

Is your device a 2DW232 or 2DW233?  I know zlymex told us not to pay much attention to the nominal current, but...

2DW232

Cheers

Alex
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #206 on: November 19, 2016, 06:43:29 AM »
Here is a one hour run result from this afternoon, the temperature probe is inside the foam enclosure but not touching the zener.

Cheers

Alex



« Last Edit: November 19, 2016, 06:45:53 AM by Alex Nikitin »
 
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Offline Kleinstein

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #207 on: November 19, 2016, 06:59:38 AM »
This does not look good at all. I might need a better adjustment of the current to get a low TC and thus less sensitivity to temperature variations. Keep in mind that the optimum current depends on the temperature - so it could be a different value with the added foam.

To check if the variations are temperature related one cold also monitor the forward diode only. This might also help to find the right current.
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #208 on: November 19, 2016, 09:13:10 AM »
Just a thought, is the Red dot on the package (if the same as zlymex's photo) added on test to indicate which diode has the most stable zener breakdown characteristics?
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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #209 on: November 19, 2016, 09:16:30 AM »
This does not look good at all.

I disagree. The temperature fluctuations are on the order of 50ppm/C or less. I didn't have time to find a better current as every time the current is changed the zener changes the temperature and it takes a while to get to the optimum point. But that is possible to resolve in various ways. Most important for me is how smooth the curve is. The LTZ1000 under similar conditions looks mush more "rugged" (though completely flat  ;) ).

Cheers

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #210 on: November 19, 2016, 09:39:39 AM »
Just a thought, is the Red dot on the package (if the same as zlymex's photo) added on test to indicate which diode has the most stable zener breakdown characteristics?

All of mine have the dot on pin 1 (near the tab).

 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #211 on: November 19, 2016, 04:41:26 PM »
Just a thought, is the Red dot on the package (if the same as zlymex's photo) added on test to indicate which diode has the most stable zener breakdown characteristics?

All of mine have the dot on pin 1 (near the tab).
That dot is used to tell parts apart when you ordered it in unmarked form. 2DW233 got a yellow dot, 2DW234 red, 2DW236 grey.
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #212 on: November 19, 2016, 10:07:12 PM »
Thanks technix, that makes more sense, I haven't seen the package part number lettering yet (maybe today with luck)  It also clears a small nagging worry that the dot might mean 'reject' (in the same way that die testers do on a wafer) :D. It looks as if the target zero Tc current for these parts will be closer to 10mA (2DW234) rather than 7.5mA then, that should save some time.
« Last Edit: November 19, 2016, 10:10:40 PM by Gyro »
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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #213 on: November 20, 2016, 03:04:58 AM »

[/quote]
That dot is used to tell parts apart when you ordered it in unmarked form. 2DW233 got a yellow dot, 2DW234 red, 2DW236 grey.
[/quote]

So, they are all marked 2DW232 and the red dot makes them a 2DW234.

Now the work begins.

Many thanks to zlymex  and VintageNut.

 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #214 on: November 20, 2016, 03:13:44 AM »

Quote
That dot is used to tell parts apart when you ordered it in unmarked form. 2DW233 got a yellow dot, 2DW234 red, 2DW236 grey.

So, they are all marked 2DW232 and the red dot makes them a 2DW234.

Wait, he didn't say that!

zlymex or technix, what does it mean when the part is marked 2DW232 *and* it has a red dot?
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #215 on: November 20, 2016, 04:29:51 AM »

Quote
That dot is used to tell parts apart when you ordered it in unmarked form. 2DW233 got a yellow dot, 2DW234 red, 2DW236 grey.

So, they are all marked 2DW232 and the red dot makes them a 2DW234.

Wait, he didn't say that!

zlymex or technix, what does it mean when the part is marked 2DW232 *and* it has a red dot?

I will confirm it with the factory next Monday. Stop using it for now though, they may be technically counterfeits.
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #216 on: November 20, 2016, 04:23:19 PM »
Just a thought, is the Red dot on the package (if the same as zlymex's photo) added on test to indicate which diode has the most stable zener breakdown characteristics?
Dotted pin is negative terminal, un-dotted pin(of 1 or 2) is positive terminal, pin 3 for reserve. This is from a datasheet.

Red dot is for 2DW232, yellow dot is for 2DW233, pink dot is for 2DW234, green dot is for 2DW235.
 
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #217 on: November 20, 2016, 05:43:12 PM »
Just a thought, is the Red dot on the package (if the same as zlymex's photo) added on test to indicate which diode has the most stable zener breakdown characteristics?
Dotted pin is negative terminal, un-dotted pin(of 1 or 2) is positive terminal, pin 3 for reserve. This is from a datasheet.

Red dot is for 2DW232, yellow dot is for 2DW233, pink dot is for 2DW234, green dot is for 2DW235.
Maybe we are referring to a different datasheet? I have obtained a full catalog from the factory and it have said none of that.
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #218 on: November 20, 2016, 05:49:45 PM »
Just a thought, is the Red dot on the package (if the same as zlymex's photo) added on test to indicate which diode has the most stable zener breakdown characteristics?
Dotted pin is negative terminal, un-dotted pin(of 1 or 2) is positive terminal, pin 3 for reserve. This is from a datasheet.

Red dot is for 2DW232, yellow dot is for 2DW233, pink dot is for 2DW234, green dot is for 2DW235.
Maybe we are referring to a different datasheet? I have obtained a full catalog from the factory and it have said none of that.

 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #219 on: November 20, 2016, 09:35:08 PM »
Just a thought, is the Red dot on the package (if the same as zlymex's photo) added on test to indicate which diode has the most stable zener breakdown characteristics?
Dotted pin is negative terminal, un-dotted pin(of 1 or 2) is positive terminal, pin 3 for reserve. This is from a datasheet.

Red dot is for 2DW232, yellow dot is for 2DW233, pink dot is for 2DW234, green dot is for 2DW235.
Maybe we are referring to a different datasheet? I have obtained a full catalog from the factory and it have said none of that.

This is definitely a different datasheet I am referring to. I have posted a translated datasheet based on what I got.
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #220 on: November 20, 2016, 11:35:57 PM »
So there are "multiple" different datasheets spreading in the wild ?  :palm:

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #221 on: November 21, 2016, 12:40:44 AM »
So there are "multiple" different datasheets spreading in the wild ?  :palm:
There are, but not contradictory, only one has slightly more information than the other.
The datasheet I was referred to(with pin dots explaination) is on the very first page of this thread.
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #222 on: November 21, 2016, 02:40:34 AM »
Unfortunately (for most of us anyway) it's in Chinese. The only English language data we have is what technix kindly translated (and even that doesn't include information on the dot significance).
« Last Edit: November 21, 2016, 02:42:30 AM by Gyro »
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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #223 on: November 21, 2016, 07:30:42 AM »
Unfortunately (for most of us anyway) it's in Chinese. The only English language data we have is what technix kindly translated (and even that doesn't include information on the dot significance).
I have contacted the factory about the dot last Friday, and at least for Shanghai No. 17 Radio Factory their dots don't signify anything regarding pins.

The one I translated is extracted from the catalog the factory provided me.
 

Offline edavid

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #224 on: November 21, 2016, 07:34:27 AM »
I have contacted the factory about the dot last Friday, and at least for Shanghai No. 17 Radio Factory their dots don't signify anything regarding pins.

The one I translated is extracted from the catalog the factory provided me.

Did you ask them about why the datasheet has the wrong pinout?
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #225 on: November 21, 2016, 07:39:56 AM »
I have contacted the factory about the dot last Friday, and at least for Shanghai No. 17 Radio Factory their dots don't signify anything regarding pins.

The one I translated is extracted from the catalog the factory provided me.

Did you ask them about why the datasheet has the wrong pinout?
The one on the first page is not their datasheet.
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #226 on: November 21, 2016, 10:21:55 AM »
I have contacted the factory about the dot last Friday, and at least for Shanghai No. 17 Radio Factory their dots don't signify anything regarding pins.

The one I translated is extracted from the catalog the factory provided me.

Did you ask them about why the datasheet has the wrong pinout?
The one on the first page is not their datasheet.
Your translation has the wrong pinout also - did that come from their datasheet?
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #227 on: November 21, 2016, 05:51:27 PM »
I have contacted the factory about the dot last Friday, and at least for Shanghai No. 17 Radio Factory their dots don't signify anything regarding pins.

The one I translated is extracted from the catalog the factory provided me.

Did you ask them about why the datasheet has the wrong pinout?
The one on the first page is not their datasheet.
Your translation has the wrong pinout also - did that come from their datasheet?
No that one is not. I measured it and put the words in a wrong way. I will fix it and reupload.
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #228 on: November 21, 2016, 11:30:35 PM »
Hmm, by far the most stable results I get are from a single zener (without the second diode in series), at about 1.4mA current and 5.246V zener voltage (the same setup as before, the resistor value is 3430 Ohm). Here is a 10min run, vertical scale 0.1ppm (0.5uV), HP3458A at NPLC100.

Cheers

Alex
« Last Edit: November 21, 2016, 11:36:51 PM by Alex Nikitin »
 
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Offline VintageNut

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #229 on: November 22, 2016, 12:14:54 AM »
My opinion is that at room temperature, the shape of the TC curve is "peaky". There may be an optimal current at room temp, but if room temp wanders even a little bit, the voltage is much too sensitive.

If the shape of the datasheet TC curve can be believed, it appears that these 2DW23X parts behave much better at 50 deg C than at room temperature.

To prove this will require some gear that at present I do not possess.

Here is what I did to satisfy my curiosity, I ran one of the 2DW parts in a banana jack mounted to the front of a KE2461. I manually searched for a current that gave as stable of a voltage as possible. The I touched the metal can. Immediately the voltage started to climb.

Another thing that may help is to create a solid copper heatsink into which the 2Dw package can be inserted.
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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #230 on: November 22, 2016, 01:07:25 AM »
Here is what I did to satisfy my curiosity, I ran one of the 2DW parts in a banana jack mounted to the front of a KE2461. I manually searched for a current that gave as stable of a voltage as possible. The I touched the metal can. Immediately the voltage started to climb.

This way you are finding a thermal balance, not a zero tempco. Try the current value about 1.4mA I've found for a single zener (the second half is not connected).

Cheers

Alex
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #231 on: November 22, 2016, 01:26:35 AM »
I can test up to 65-70C for theories above ;)
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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #232 on: November 22, 2016, 02:31:00 AM »
I can test up to 65-70C for theories above ;)

...and you write Ninja Python code. You can create an automatic characterization program and save a mountain of data.
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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #233 on: November 22, 2016, 02:58:38 AM »
You might want to try going to a much higher current in the series zener+diode mode. One of my samples is shifting by around 10uV when subjected to the cold finger test while running at 20mA.  That's very roughly the same order of shift as I see in my 1N829A at it's nominal zero Tc current (8mA).
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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #234 on: November 22, 2016, 03:13:26 AM »
I can test up to 65-70C for theories above ;)

...and you write Ninja Python code. You can create an automatic characterization program and save a mountain of data.
Maybe I will try the automated characterization process if I know hoe to get good measurement, and give you guys an updated translated datasheet with some measured data points.
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #235 on: November 22, 2016, 03:22:03 AM »
You might want to try going to a much higher current in the series zener+diode mode. One of my samples is shifting by around 10uV when subjected to the cold finger test while running at 20mA.  That's very roughly the same order of shift as I see in my 1N829A at it's nominal zero Tc current (8mA).

Did you wrap the device to reduce air flow over the device?
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Offline Kleinstein

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #236 on: November 22, 2016, 03:32:24 AM »
Hmm, by far the most stable results I get are from a single zener (without the second diode in series), at about 1.4mA current and 5.246V zener voltage (the same setup as before, the resistor value is 3430 Ohm). Here is a 10min run, vertical scale 0.1ppm (0.5uV), HP3458A at NPLC100.

This is very interesting. So it looks like one can also use it as a 5.2-5.3 V reference at lower current. For some applications this can be the more interesting operating point, as it is lower power and a divider from 5.3 V to 5 V (or 10.5 V to 10 V) is less sensitive to resistor drift as one from 6 or 7 V. Reducing the sensitivity of the resistors by something like a factor of 5 can be a really big advantage.

Even with this lower power, it looks really low noise and stable. For most application this can be good enough - hard to find something with lower noise. You have to take into account that some of the noise in the curve could be still the LTZ1000 inside the 3458.

The curve shape with a maximum in voltage over temperature will likely exist at all currents. Changing the current will shift the maximum and thus the temperature with zero linear TC to different temperatures. So there is likely nothing special with the 50-60C temperature where the curve in the DS has its maximum. Finding the compensating current is finding the curve where the maximum (and thus zero slope) is at the working temperature.

Choosing a higher, regulated temperature (which might end up at 50 C because this a practical temperature) is attractive as in the horizontal region of the curve there is no need for a super stable temperature.

 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #237 on: November 22, 2016, 05:51:56 AM »
You might want to try going to a much higher current in the series zener+diode mode. One of my samples is shifting by around 10uV when subjected to the cold finger test while running at 20mA.  That's very roughly the same order of shift as I see in my 1N829A at it's nominal zero Tc current (8mA).

Did you wrap the device to reduce air flow over the device?

Sorry, got called away. That was free-air, I wasn't looking for precise results, just trying to find a turnover point. I was driving it in Zener+diode mode (dot pin -ve), via a 1k resistor. Applying a cold finger was causing an increase in voltage up to about 26V input, above 27V input it turned over and started dropping instead. At about 26.5V it seemed to reach equibrium (~10uV shift). At all times the device felt warm / hot so I was always applying a cooling effect.

Not a particularly scientific test I know, but I was getting fed up with seeing large (100uV or more) shifts when I touched the package and decided to just keep ramping up the current to see what happened. 20mA was way above the current I was expecting to apply. I haven't yet tried the same on other devices to see how repeatable this is - this current is uncomfortably close to the 30mA Iz Max.

Edit: Maybe this is the current level needed to hit 50'C package temperature in free-air, so you could maybe achieve the same result at lower current if package is thermally insulated.
« Last Edit: November 22, 2016, 05:55:29 AM by Gyro »
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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #238 on: November 22, 2016, 06:18:53 AM »
Maybe I will try the automated characterization process if I know hoe to get good measurement, and give you guys an updated translated datasheet with some measured data points.

Please delete the 1st translated datasheet, as it may mislead future readers.

And post the original datasheet here that you got from the manufacturer, even its in Chinese, at least Zlymex can verify your translation.

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #239 on: November 22, 2016, 06:53:03 AM »
Maybe I will try the automated characterization process if I know hoe to get good measurement, and give you guys an updated translated datasheet with some measured data points.

Please delete the 1st translated datasheet, as it may mislead future readers.

And post the original datasheet here that you got from the manufacturer, even its in Chinese, at least Zlymex can verify your translation.
I will delete the original translation if you find it misleading. Keep in mind that this is the very first sentence an instructor will tell every Chinese EE student: do not trust in datasheets blindly, characterize everything yourself before using it.

Those parts made under Chinese traditional part numbering systems can (when talking parts made before the mid-80s the word would be "very likely will") vary from piece to piece as the standards is extremely lax. So if you are using parts in Chinese part numbering system, measure it before even thinking about using it, as you may be in for a surprise, especially when talking about older parts.

The discrepency between the datasheet Zlymex posted and the pinout the factory told me (not in the original datasheet - I had to phone in to confirm) is a clear indication of this problem.
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #240 on: November 22, 2016, 07:14:37 AM »
Using the finger to test the sensitivity to temperature can be a little misleading: there are two point where the finger will not cause a change: one is when the TC of the device is zero and a second is when the device temperature is the same as the finger, so there will be no more change in temperature.
 
Increasing the current will also increase the temperature, so one is probing at different temperatures, not just different currents. It depends on the thermal design how those two parameters are combined.

From the turn on transients the VintageNut did, the TC seems to turn more negative at higher current. It is still the question if this due to the higher temperature or due to the higher current. The test is still useful to find the suitable current for the given thermal conditions. However one tends to look at the changes below (before) equilibrium temperature. So it is not the most accurate way.
Form the curved shape of the curve in the DS it is suggested that a higher temperature gives a more negative TC. If the DS curve can be believed this would be something like -0.2 ppm/K². So a self heating of 10 K would change the TC by about -2 ppm/K.

Without a good DS, the logical thing would be to measure the curves you would wish to have in a good DS.
To get data relative to the true chip temperature one could use the normal diode as an approximate temperature sensor. This would need 2 voltmeters and likely an external heater. The DMM for the normal diode voltage (-> temperature) does not need to be that accurate, but the one for the zener voltage should be. So it would be first to check the forward diode with current only through that diode (to reduce self heating), or maybe use the start of transient. Than with the same current one could test on increasing temperature. So raw data would be zener voltage versus diode voltage.

The measurements from Alex Nikitin suggest, the using only one diode (and lower current) might be the even more interesting operation point.
 
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Offline VintageNut

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #241 on: November 22, 2016, 01:11:58 PM »
I drilled a hole in a solid copper plate and placed a 2DW232 inside the hole and mounted that on the front of the KE2461. Using 3mA, after a long stabilization period, the short term standard deviation is 2uV. That looks promising.

I still think that running this device close to 50C will give the best long term stability.

I am looking forward to someone having a proposed method of ovenizing this device. 
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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #242 on: November 22, 2016, 02:28:35 PM »
Thank you Zlymex and VintageNut for letting me play in these reindeer games :)

I've been working on a little temperature controlled test environment and put it to work this weekend running tests on one of the ones
I got, hunting for an inflection point in the temperature response. I ran it at various currents from 3mA to 18mA, changing the temperature of the chamber from 23C to 40C.  Consistent with the findings of others in this thread, the TC did not change sign in this interval, with the smallest tempco being at 18mA.  (I observed roughly 25ppm/C at 18mA. Even though the test wasn't set up to accurately measure TC, it still seemed like a pretty linear temperature response from 23 to 35C at that current.) 

I don't know what the die temperatures were, since I haven't done a pulsed current test yet.  (I need a different setup to take measurements fast enough.)

I just got some enameled nichrome wire, so I'm going to try to turn one of things into a little oven and see if I can find the temperature response curve from the datasheet.  Then I can use the zener voltage at that zero point to stabilize it.
I am but an egg
 
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Offline Galaxyrise

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #243 on: November 22, 2016, 06:30:04 PM »
I got things set up and did a fairly extreme temperature excursion at 5mA (I raised the outside to about 113C, though the die temperature was certainly much lower.)  The zener voltage followed a curve not unlike the datasheet.  However, the zener's parabola was only just barely visible in the total voltage; the magnitudes of the temperature coefficients is that different at 5mA.

Last thing I did before bed was to bump the current up to 10mA.  I did not have the time to do this one properly, but I did not see an inflection point in the zener voltage any more (dV stayed positive for the entire test), and the overall TC looked much less.

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #244 on: November 22, 2016, 10:47:01 PM »
Here are the overnight results with a single zener and 1.38mA current. The tempco is about -6ppm/C, the noise is low and the stability looks good. 2ppm/div vertical scale on Volts.

Cheers

Alex
« Last Edit: November 22, 2016, 10:55:06 PM by Alex Nikitin »
 
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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #245 on: November 22, 2016, 11:06:50 PM »
This is good information. Here is what I see. For most of this time span, the voltage is rising despite what is happening with temperature. At around 08:00, the voltage is stable. After stability is reached, the zener voltage responds to temperature change in the opposite direction of the temperature change.

This long time to warm up is what I have seen operating the device in its intended configuration. If the device is operated at a temperature much higher than ambient, then the warmup time should be eliminated.



Here are the overnight results with a single zener and 1.38mA current. The tempco is about -6ppm/C, the noise is low and the stability looks good. 2ppm/div vertical scale on Volts.

Cheers

Alex
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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #246 on: November 22, 2016, 11:20:32 PM »
This is good information. Here is what I see. For most of this time span, the voltage is rising despite what is happening with temperature. At around 08:00, the voltage is stable. After stability is reached, the zener voltage responds to temperature change in the opposite direction of the temperature change.

This long time to warm up is what I have seen operating the device in its intended configuration. If the device is operated at a temperature much higher than ambient, then the warmup time should be eliminated.

At 1.4mA the dissipation is only 7mW, so not much to warm up with. The temperature readings are not for the zener itself, but for the enclosure, that might explain the discrepancies. I will try next time to log the voltage on the second zener in a diode connection, that would give a very good tracking of the actual zener temperature.

Cheers

Alex
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #247 on: November 23, 2016, 12:01:15 AM »
This is good information. Here is what I see. For most of this time span, the voltage is rising despite what is happening with temperature. At around 08:00, the voltage is stable. After stability is reached, the zener voltage responds to temperature change in the opposite direction of the temperature change.

This long time to warm up is what I have seen operating the device in its intended configuration. If the device is operated at a temperature much higher than ambient, then the warmup time should be eliminated.

At 1.4mA the dissipation is only 7mW, so not much to warm up with. The temperature readings are not for the zener itself, but for the enclosure, that might explain the discrepancies. I will try next time to log the voltage on the second zener in a diode connection, that would give a very good tracking of the actual zener temperature.

Cheers

Alex

I do not see any discrepancies. I see the zener voltage rising to some asymptotic voltage despite any ups and downs of temperature. If this is not "warm up" then it is some other march toward some sort of equilibrium that appears to be achieved at 08:00 where temperature is flat and voltage is flat. During that flat time, zener voltage and temperature appear to be at equilibrium.
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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #248 on: November 23, 2016, 12:10:10 AM »
I do not see any discrepancies. I see the zener voltage rising to some asymptotic voltage despite any ups and downs of temperature. If this is not "warm up" then it is some other march toward some sort of equilibrium that appears to be achieved at 08:00 where temperature is flat and voltage is flat. During that flat time, zener voltage and temperature appear to be at equilibrium.

Hmm, what I see is that the temperature is steadily falling (with some variations on the temperature sensor which may not necessarily affect the zener - as I've said, the temperature sensor is not in a direct contact with the zener). More important for me is the fact that the voltage comes back to exactly the same value at the end of the run at 25C as it was at the very beginning (less than 1ppm difference).

Cheers

Alex
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #249 on: November 23, 2016, 01:28:03 AM »
Hmm, what I see is that the temperature is steadily falling (with some variations on the temperature sensor which may not necessarily affect the zener - as I've said, the temperature sensor is not in a direct contact with the zener). More important for me is the fact that the voltage comes back to exactly the same value at the end of the run at 25C as it was at the very beginning (less than 1ppm difference).

Cheers

Alex

Alex,
Could you post the raw figures for that run please? I'd like to run some statistics on them.
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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #250 on: November 23, 2016, 01:49:41 AM »
Hmm, what I see is that the temperature is steadily falling (with some variations on the temperature sensor which may not necessarily affect the zener - as I've said, the temperature sensor is not in a direct contact with the zener). More important for me is the fact that the voltage comes back to exactly the same value at the end of the run at 25C as it was at the very beginning (less than 1ppm difference).

Cheers

Alex

Alex,

Could you post the raw figures for that run please? I'd like to run some statistics on them.


Here. It includes several step changes in the current at the very beginning which I've cut off of the uploaded graph. Steps in the resistor value are 3.449K, 3.448K, 3.446K and 3.447K (at that value the main overnight test was run).

Cheers

Alex

« Last Edit: November 23, 2016, 01:56:24 AM by Alex Nikitin »
 
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Offline Seekonk

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #251 on: November 23, 2016, 02:20:18 AM »
For thermal mass, this defective press in triac jumped out of the junkbox.  Dug out the old part and potted it in this 3/4 inch slug.
Large nut would also work.
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #252 on: November 23, 2016, 03:06:48 AM »
Using the same sample as I was using yesterday (the 20mA run), I am seeing the same stable point as Alex for the Zener alone... 1.4mA, 5.251V. This appears to be another turnover point: Negative TC below, Positive TC above. My sample seems to hold within about 20uV over a range between 20-24'C.

I guess the two turnover points make some kind of sense, the higher the current the more positive the TC of the zener becomes until it matches the negative TC of the diode, but not until about 20mA. Much higher than the expected 5 - 7.5mA. Below 20mA it seems that the positive TC slope of the zener is too low. [Edit:] I'm assuming that the TC of the diode will remain pretty much -0.6mV/'C regardless of current.

A solution (if achieving lower noise than at 1.4mA operation is a priority) may be to add a divided down portion of the diode forward drop to the zener voltage. Maybe this could be done by biasing the diode separately and using passive divider?

One other thing. Has anyone else noticed that the leads seem to be made of rather stiff grade magnetic steel? I've avoided risking my good cutters on them but even my carbide ones take a bit of force. There also seems to be a bit of crazing on the glass to metal seals of most samples, possibly due to the lead length and stiffness. I think they will need mounting with care to avoid stresses.
« Last Edit: November 23, 2016, 03:11:00 AM by Gyro »
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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #253 on: November 23, 2016, 03:28:20 AM »
[Edit:] I'm assuming that the TC of the diode will remain pretty much -0.6mV/'C regardless of current.

Isn't it -2.2 ... -2.5mV/C ?

Cheers

Alex
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #254 on: November 23, 2016, 03:46:51 AM »
Oops!  :-[

Can't think now why that figure is sticking in my (somewhat defective) head!
« Last Edit: November 23, 2016, 03:50:27 AM by Gyro »
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Offline Kleinstein

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #255 on: November 23, 2016, 04:10:23 AM »
For most cases I would prefer the 1.4 mA operation point. The noise already seems to be low (e.g. much better than an LM329 or LM399), possibly at the level an LTZ1000 would get at 5 mA. If you really care, just use 2 in parallel or series - not that expensive and still low power.

Also the 5.25 V level could be a big plus if one wants to scale to 5 V (or 10 V starting from 2 diodes in series).

Adding only a part of the diode drop should work to get a different operating point (higher current) for compensation. I don't even think one would need separate biasing - just a divider to get something like half the diode voltage.
 
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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #256 on: November 23, 2016, 04:47:47 AM »
True, if it performs so well at low current there really isn't any need to go higher.

Quote
Adding only a part of the diode drop should work to get a different operating point (higher current) for compensation. I don't even think one would need separate biasing - just a divider to get something like half the diode voltage.

Actually, yes, it is that simple isn't it, I was over-thinking it.  Correcting by balancing a Positive TC with an adjustable negative TC (assuming relatively flat profiles) just feels a little more comfortable than relying on the TC turnover point of the zener alone, at least both slopes are going in predictable directions. Maybe this has the possibility of yielding a lower overall TC over a wider temperature range, it might on the other hand be needless (drift introducing) added complexity. It seems worth a try though.
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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #257 on: November 23, 2016, 05:56:11 AM »
For some reason I'm having problems with file uploads to the forum today; so you're not going to get any charts.

I've taken a look at the figures Alex kindly uploaded. Doing a linear regression of voltage against temperature gives a tempco of -24.3 ppm/C with a correlation coefficient (R2) of 0.76 which is a fairly strong correlation. On a scatter plot there are 3 islands of outliers, all well away from the main line. The scatter plot suggests that relatively there's a lot of noise in the temperature readings.
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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #258 on: November 23, 2016, 08:28:59 AM »
@Cerebus
If I look at the graph from previous page I would say that an app. 5.25V reference level and app. -60uV (min/max) in 2.5C (min/max) would make app -5 to -6 ppm/C (as Alex already said).
Why don't your numbers come close to that?

If this is quite good lineair, as you also say, then the TC could be indeed nicely compensated, like Giro proposes by a divider like this one (with different numbers) of Zlymex:
http://www.eevblog.com/forum/metrology/spread-sheet-aided-design-of-compensation-for-7v-to-10v-step-up-resistor-set/
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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #259 on: November 23, 2016, 02:04:20 PM »
@Cerebus
If I look at the graph from previous page I would say that an app. 5.25V reference level and app. -60uV (min/max) in 2.5C (min/max) would make app -5 to -6 ppm/C (as Alex already said).
Why don't your numbers come close to that?

If this is quite good lineair, as you also say, then the TC could be indeed nicely compensated, like Giro proposes by a divider like this one (with different numbers) of Zlymex:
http://www.eevblog.com/forum/metrology/spread-sheet-aided-design-of-compensation-for-7v-to-10v-step-up-resistor-set/

I didn't imply anything about the linearity. Are you perhaps confused by the mention of a linear regression? I'm not saying that the tempco is X, just that X is what pops out of a linear regression of this narrow temperature range. A linear regression seems reasonable (as opposed to other curve fits) as, for the small temperature span in Alex's figures, the curve is quite linear - over a wider temperature I'd expect it to be more polynomial in nature. The disparity from more empirically arrived at figures is in part the small range and in part the sheer amount of noise in the temperature data - the latter makes it difficult to really see what's going on, precisely why I wanted to try some numerical methods. I wish I could fix my uploading problem as the scatter diagram is quite informative, there's a lot of smearing across temperature but there's also a very clear central trend. It might be beginning to flatten out at lower temperatures but, again, the noise in the temperature data makes that unclear.

I actually spent the evening hacking about some foam, a peltier device, a couple of heatsinks, a thermocouple, a breadboard and a ZIF socket, to see if I could come up with a fixture that makes for a more controlled testing environment - I'm perhaps 20% of the way there.
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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #260 on: November 24, 2016, 12:33:23 AM »
Here is a graph of many hours overnight at 6mA mounted to a copper bar on the front of a KE2461. The graph starts during the day when the sun is shining into my office/lab. This device appears to be a candidate as a temperature sensor.

« Last Edit: November 24, 2016, 12:39:10 AM by VintageNut »
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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #261 on: November 24, 2016, 01:14:34 AM »
For some reason I'm having problems with file uploads to the forum today; so you're not going to get any charts.

I've taken a look at the figures Alex kindly uploaded. Doing a linear regression of voltage against temperature gives a tempco of -24.3 ppm/C with a correlation coefficient (R2) of 0.76 which is a fairly strong correlation. On a scatter plot there are 3 islands of outliers, all well away from the main line. The scatter plot suggests that relatively there's a lot of noise in the temperature readings.

Is it -24.3 ppm/C or -24.3 uV/C (which is about -5ppm/C)?

Cheers

Alex
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #262 on: November 24, 2016, 01:37:01 AM »
For some reason I'm having problems with file uploads to the forum today; so you're not going to get any charts.

I've taken a look at the figures Alex kindly uploaded. Doing a linear regression of voltage against temperature gives a tempco of -24.3 ppm/C with a correlation coefficient (R2) of 0.76 which is a fairly strong correlation. On a scatter plot there are 3 islands of outliers, all well away from the main line. The scatter plot suggests that relatively there's a lot of noise in the temperature readings.

Is it -24.3 ppm/C or -24.3 uV/C (which is about -5ppm/C)?

Cheers

Alex

It's just the m in y = mx + c, where y is volts and x is Celsius so, yes, it's effectively uV/C. Sorry, I should have been clearer but it was getting late here.
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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #263 on: November 24, 2016, 03:26:45 AM »
Here is a graph of many hours overnight at 6mA mounted to a copper bar on the front of a KE2461. The graph starts during the day when the sun is shining into my office/lab. This device appears to be a candidate as a temperature sensor.

At 6 mA the TC of the zener is supposed to about compensate with the TC of the normal diode. So no wonder you get a lot of sensitivity to temperature variations with just the zener, should be somewhere in the +1-2mV/K range. So the 160 µV of voltage change would correspond to something like 0.1-0.2 K.

There should be no need for an external compensation of the linear TC. It should be possible to to find an operating current where the linear TC tends towards zero for a given temperature. There even seem to be two such current settings. One low (e.g. 1mA range) for just the zener and one rather high (e.g. 10 mA, but could be 5-20 mA depending on sample) for the series configuration. It just seems to be a little tricky to find one of those points, especially the one at higher current.

The 5 ppm/K (at 1.4 mA) is already a useful value / not that bad. To get a rough idea one would need TC data for a few different currents - to get an idea on how accurate one should find that ideal current. The curves with an external temperature sensor are not that accurate - so it would be really preferred to use the internal diode as a temperature sensor - at least for relative changes.
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #264 on: November 24, 2016, 03:51:03 AM »
It is being operated with both diodes in series. Looking for the current that produces the least swings in voltage for ambient temperature in my office/lab.


Here is a graph of many hours overnight at 6mA mounted to a copper bar on the front of a KE2461. The graph starts during the day when the sun is shining into my office/lab. This device appears to be a candidate as a temperature sensor.

At 6 mA the TC of the zener is supposed to about compensate with the TC of the normal diode. So no wonder you get a lot of sensitivity to temperature variations with just the zener, should be somewhere in the +1-2mV/K range. So the 160 µV of voltage change would correspond to something like 0.1-0.2 K.

There should be no need for an external compensation of the linear TC. It should be possible to to find an operating current where the linear TC tends towards zero for a given temperature. There even seem to be two such current settings. One low (e.g. 1mA range) for just the zener and one rather high (e.g. 10 mA, but could be 5-20 mA depending on sample) for the series configuration. It just seems to be a little tricky to find one of those points, especially the one at higher current.

The 5 ppm/K (at 1.4 mA) is already a useful value / not that bad. To get a rough idea one would need TC data for a few different currents - to get an idea on how accurate one should find that ideal current. The curves with an external temperature sensor are not that accurate - so it would be really preferred to use the internal diode as a temperature sensor - at least for relative changes.
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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #265 on: November 24, 2016, 03:55:17 AM »
It is being operated with both diodes in series. Looking for the current that produces the least swings in voltage for ambient temperature in my office/lab.

For both diodes in series and 6mA current the voltage is very low!

Cheers

Alex
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #266 on: November 24, 2016, 03:57:01 AM »
I've been playing around with the divider approach today and it looks as if it is possible to achieve very low TC values over a limited temperature range even with a simple hook up. I've attached the schematic for clarity but it's basically just taking the output voltage from a divider tap across the forward biased diode. I simply used a 2k cermet preset, it took a little tweaking but it looks as if the flat portion of the TC curve can be adjusted to any temperature and operating current, in this case about 23'C and is very flat over a few degrees. TC is sensitive to both divider ratio and supply current as you would expect.

Operating the device at 5.010mA with the divider (pot) measuring 765R / 1k3 the output of my sample is 5.878V  Temperature profile came out as follows (values relative to 23'C case temperature):

20'C     -12uV
20.5'C  -4uV
21'C     -3uV
21.5'C  -2uV
22'C     -1uV
22.5'C   0
23'C      0
23.5'C   -1uV
24'C      -5uV
24.5'C   -7uV
25'C      -14uV

Temperatures were measured during device warm-up (it finally settled at about 25.3'C) using a thermocouple taped to the side of the can. I was using a Geller SVR-T and Muirhead decade divider with Datron 1041M, null meter style. I repeated 3 times, each warm-up taking less than 5 mins, with consistent results (obviously the readings were a bit noisy at this level).
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Offline VintageNut

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #267 on: November 24, 2016, 03:59:49 AM »
It is being operated with both diodes in series. Looking for the current that produces the least swings in voltage for ambient temperature in my office/lab.

For both diodes in series and 6mA current the voltage is very low!

Cheers

Alex


Pilot error. I grabbed the wrong one. i have 4 of these mounted to banana plugs. One is wired for just the one diode. Arrrggghhh
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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #268 on: November 24, 2016, 08:43:43 AM »
I've been playing around with the divider approach today and it looks as if it is possible to achieve very low TC values over a limited temperature range even with a simple hook up. I've attached the schematic for clarity but it's basically just taking the output voltage from a divider tap across the forward biased diode. I simply used a 2k cermet preset, it took a little tweaking but it looks as if the flat portion of the TC curve can be adjusted to any temperature and operating current, in this case about 23'C and is very flat over a few degrees. TC is sensitive to both divider ratio and supply current as you would expect.

Operating the device at 5.010mA with the divider (pot) measuring 765R / 1k3 the output of my sample is 5.878V  Temperature profile came out as follows (values relative to 23'C case temperature):

20'C     -12uV
20.5'C  -4uV
21'C     -3uV
21.5'C  -2uV
22'C     -1uV
22.5'C   0
23'C      0
23.5'C   -1uV
24'C      -5uV
24.5'C   -7uV
25'C      -14uV

Temperatures were measured during device warm-up (it finally settled at about 25.3'C) using a thermocouple taped to the side of the can. I was using a Geller SVR-T and Muirhead decade divider with Datron 1041M, null meter style. I repeated 3 times, each warm-up taking less than 5 mins, with consistent results (obviously the readings were a bit noisy at this level).

It's now 5 hours later... The room has cooled a couple of degrees so the package temperature has dropped to 23.7'C. The voltage is now +3uV from the previous 23.5'C value (+7uV from the previous 24'C value). Operating current is still sitting at 5.010mA and there has been plenty of time for any thermocouple effects to stabilise.

It probably says as much about the SVR-T's TC and the Muirhead's ratio stability as it does about the sample but that's pleasingly close. Either that or everything is drifting rather conveniently in the same direction. Surprising though. :D


EDIT: Probably happy chance above. One hour later, case temperature is now 22.9'C and voltage -6uV vs previous 23'C reading. Room temperature has dropped quite fast now the heating has gone off though, so the higher thermal mass items probably aren't keeping pace. I'm off the edge of my measurement capability here.
« Last Edit: November 24, 2016, 09:47:18 AM by Gyro »
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Offline TiN

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #269 on: November 25, 2016, 12:19:54 AM »
First candy test. Nothing fancy, just K2400 run with help of little snake.



Blue line - pin2-pin3 junction
Orange line - pin1-pin2 junction

Voltage sourced -10 to +10V, current compliance 20mADC

DATA 1 (XLS)
DATA 2 (XLS)
« Last Edit: November 25, 2016, 03:43:08 AM by TiN »
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Offline evb149

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #270 on: November 25, 2016, 01:10:55 AM »
Thank you.
That's interesting so if I'm understanding this right:
pin 1-pin2 is something like a *back to back" zener with a roughly symmetric +/-6.2VDC breakdown in each applied polarity

pin2-pin3 is something that basically looks like a VBE junction of a small signal BJT with forward conduction of roughly 1 VBE and a reverse zener breakdown of 5.2V.

I had no idea from my understanding of the diagram in the datasheet that the device behaved like this.  I was expecting symmetrical back to back zeners of identical characteristics with a common center point, similar to what you show between pin1-pin2 if you neglect the middle common lead entirely.

Is this your interpretation of your test results or am I misunderstanding your setup? 

EDIT: I guess pin2-pin3 behaves like a normal 5.4VDC zener which is a single device with the usual non-symmetric VF/VR (which is like a BJT VBE but no need to otherwise liken it to a BJT)

So really this thing is behaving like
PIN1---[K-D1-A][A-D2-K]--PIN2--[D3]---PIN3
...with D1,D2 = (6.2-VF) volt zeners back to back, D3=5.4V single zener with perhaps my being incorrect in stating the A, K designations.
 
So you could either operate it as
A: a single (ZENER+DIODE series ) PIN1-[D1+D2]-PIN2: 6.2V overall
B: a single ZENER (5.4V reverse polarity) PIN2-PIN3 of a certain polarity.
C: a single DIODE (VF forward polarity) PIN2-PIN3 of the other polarity.

And if you measure from PIN1---PIN3 I guess you get VZ(D1)+VF(D2)+VF(D3) or something like that depending on your applied polarity?  In which case you'd expect the double VF tempco of D2+D3 is designed to balance the D1 VZ tempco, or maybe PIN2-PIN3 is meant to be independently used only for temperature monitoring/control and the reference taken only from PIN1-PIN2.



First candy test. Nothing fancy, just K2400 run with help of little snake.



Blue line - pin2-pin3 junction
Orange line - pin1-pin2 junction

Voltage sourced -10 to +10V, current compliance 20mADC

DATA 1 (XLS)
DATA 2 (XLS)
« Last Edit: November 25, 2016, 01:26:40 AM by evb149 »
 

Offline TiN

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #271 on: November 25, 2016, 01:13:10 AM »
Yea, correct.
I'll have to try pin 1-3 too :)

Zoom in region +/-1nA :

« Last Edit: November 25, 2016, 03:42:16 AM by TiN »
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Offline 2N3055

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #272 on: November 25, 2016, 02:32:40 AM »
Yea, correct.
I'll have to try pin 1-3 too :)

It should be the same...
 

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #273 on: November 25, 2016, 03:55:27 AM »
First candy test. Nothing fancy, just K2400 run with help of little snake.



Blue line - pin2-pin3 junction
Orange line - pin1-pin2 junction

Voltage sourced -10 to +10V, current compliance 20mADC

DATA 1 (XLS)
DATA 2 (XLS)

How long did this trace take and in what order did you measure the parameters (back to back zeners vs the single zener trace)? Unfortunately device (junction) temperature is the important factor rather than ambient temperature. If the device temperature changed at all during the sweep then the characteristics will have been changing too. There is little data in the critical conduction areas, where Temperature coefficients of the forward and reverse biased zeners are so critical. If you read back through the posts you will see that Alex found a TC turnover point at 1.4mA for the Zener alone and I found another at 20mA for series Zener and forward biased Zener (diode) at 20mA. I can't see either showing up on the sweep (although at -20mA it may just be visible at the botton left of the trace), also the slopes on the left and right of the trace are different too (right hand one is shallower with no hint of turnover visible), when I would have expected them to be near identical this makes me think that device temperature was changing,

EDIT: Sorry, I think I'm getting tangled up between I/V curves with TC.  :palm: Something still doesn't look right in comparison between the bottom left and top right slopes though (back to back Zeners).
« Last Edit: November 25, 2016, 04:40:39 AM by Gyro »
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Offline SvanGool

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #274 on: November 25, 2016, 04:00:59 AM »
@TiN
Could it be that either 1-3 or 2-3 is inverted (otherwise you have two zeners in the same direction, which is not the case according 1-2)?
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Offline VintageNut

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #275 on: November 25, 2016, 05:43:58 AM »
Be aware that when you sweep across a sign change, the instrument is on two completely different ranges.

If you want to rule out different range offsets and/or different range linearities, only sweep from 0V to 10V then reverse the banana plugs at the SMU and then run the 0 to 10V sweep again. Now you have the full characterization and only use one range of the SMU.

Also, when you sweep from -10V to +10V continuously, the device is decreasing voltage (and heat) in the first half of the sweep and increasing voltage (and heat) in the second half of the sweep.

Sweeping from 0V to 10V for both halves of the curve may reduce the difference in heating as well.

These devices are very sensitive to change in temperature.
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Offline Cerebus

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #276 on: November 25, 2016, 07:28:54 AM »
Be aware that when you sweep across a sign change, the instrument is on two completely different ranges.

Why do you think that?

Unlike some of the other 2xxx range of instruments, I don't have schematics for the Keithley 2400 but I'd be surprised if it doesn't use the same current balancing integrating ADC that the other 2xxx series instruments do and the 'source' side of things is explicitly called out as 4 quadrant in the specifications.
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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #277 on: November 25, 2016, 08:23:16 AM »
Be aware that when you sweep across a sign change, the instrument is on two completely different ranges.

Why do you think that?

Unlike some of the other 2xxx range of instruments, I don't have schematics for the Keithley 2400 but I'd be surprised if it doesn't use the same current balancing integrating ADC that the other 2xxx series instruments do and the 'source' side of things is explicitly called out as 4 quadrant in the specifications.

The calibration report with data would be the definitive document.

TiN, did you have your K2400 calibrated? Do you have the data report?

Attached is the pertinent info from a 2450 that I used. Source +10V actual is 10.00022. Source -10V actual is -9.99997

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Offline Cerebus

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #278 on: November 25, 2016, 09:08:52 AM »
Be aware that when you sweep across a sign change, the instrument is on two completely different ranges.

Why do you think that?

Unlike some of the other 2xxx range of instruments, I don't have schematics for the Keithley 2400 but I'd be surprised if it doesn't use the same current balancing integrating ADC that the other 2xxx series instruments do and the 'source' side of things is explicitly called out as 4 quadrant in the specifications.

The calibration report with data would be the definitive document.

TiN, did you have your K2400 calibrated? Do you have the data report?

Attached is the pertinent info from a 2450 that I used. Source +10V actual is 10.00022. Source -10V actual is -9.99997

You said "two completely different ranges" and I want to understand why you think that and if indeed that is the case. The calibration points aren't evidence of that, just of one range with 30uV offset and 19 ppm gain errors (and doubtless some linearity error too) unless there's something about the way the K2400 works that you know and that I don't.
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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #279 on: November 25, 2016, 09:25:40 AM »
I'll calibrate and generate report for you once get back, no problem. I calibrated it some year ago, and two years before it was calibrated by Tek Taiwan. Here's that old report.

I'm out from lab next 5 days. I don't think this basic test suffer much from SMU specs. Sweep was rather fast,  ~2minutes total, with 5mV increments. I can run sweeps with 3458 as sampler, that shall fix linearity issue? :)

My plan for next step is to mount diode to copper slug, put YSI 44008 thermistor on it and attach to TEC for controlling temperature. Then I can run much slower sweeps with focus just in zener regions with temperature points from +15 to +65 in 1C step. Pretty sure can do 0.005C stability with the setup.
« Last Edit: November 25, 2016, 09:36:15 AM by TiN »
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Online Gyro

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #280 on: November 25, 2016, 09:50:41 AM »
Has anyone tried duplicating the voltage divider TC compensation adjustment that I posted?

Given that the connection between the zener and the forward biased diode/zener is brought out (unlike a 1N82x for instance) then I can only assume that this is how TC adjustment would normally be implemented (unless every application runs it at 50'C). Whilst running with an individual zener biased at 1.4mA appears workable, this doesn't tie up with any of the listed datasheet parameters.
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Offline VintageNut

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #281 on: November 25, 2016, 10:06:28 AM »
Be aware that when you sweep across a sign change, the instrument is on two completely different ranges.

Why do you think that?

Unlike some of the other 2xxx range of instruments, I don't have schematics for the Keithley 2400 but I'd be surprised if it doesn't use the same current balancing integrating ADC that the other 2xxx series instruments do and the 'source' side of things is explicitly called out as 4 quadrant in the specifications.

The calibration report with data would be the definitive document.

TiN, did you have your K2400 calibrated? Do you have the data report?

Attached is the pertinent info from a 2450 that I used. Source +10V actual is 10.00022. Source -10V actual is -9.99997

You said "two completely different ranges" and I want to understand why you think that and if indeed that is the case. The calibration points aren't evidence of that, just of one range with 30uV offset and 19 ppm gain errors (and doubtless some linearity error too) unless there's something about the way the K2400 works that you know and that I don't.

No, I don't have special knowledge. I look at the calibration report and see that the + and - source have a different measured value absolute value. So, even if a device being measured were perfectly symmetric in its behavior for + and - voltage, the 2400 would not necessarily plot a symmetric curve.

The best thing to do would be to plot curves that are the measured values with the uncertainties added and subtracted. You have three curves. The measured curve and the curves that represent the most negative uncertainty and the most positive uncertainty. You cannot know symmetry any better than the min and max uncertainty curves.

In practice, most of the keithley gear is far better than the worst-case specifications. To know if and how much better, you have to perform some tests to quantify the offset and noise of the range being used.
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Offline TiN

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #282 on: November 25, 2016, 10:12:09 AM »
I'd expect changes from selfheating in diodes would be magnitude more than this error from SMUs ADC (which is almost a clone of K2000). Anyway, running same sweep with 3458 in parallel is no difficulty.
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Offline VintageNut

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #283 on: November 25, 2016, 10:15:28 AM »
I'd expect changes from selfheating in diodes would be magnitude more than this error from SMUs ADC (which is almost a clone of K2000). Anyway, running same sweep with 3458 in parallel is no difficulty.

Excellent. For symmetry of self heating I suggest starting at 0V and sweeping to 10V, maybe pause for some recovery and then sweep from 0 to -10V.
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Offline plesa

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #284 on: November 25, 2016, 10:24:28 AM »
I'd expect changes from selfheating in diodes would be magnitude more than this error from SMUs ADC (which is almost a clone of K2000). Anyway, running same sweep with 3458 in parallel is no difficulty.

Excellent. For symmetry of self heating I suggest starting at 0V and sweeping to 10V, maybe pause for some recovery and then sweep from 0 to -10V.

Keithley 2400 has pulse option, which will eliminate self heating. Similar way I measured parameters of LTZ1000 on 2636B.
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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #285 on: November 25, 2016, 10:29:33 AM »
I was thinking of pulsed sweeps too. I believe 4142B SMU has pulsed modes natively.
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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #286 on: November 25, 2016, 01:16:46 PM »
I was thinking of pulsed sweeps too. I believe 4142B SMU has pulsed modes natively.

Pulse mode measurement usually is much smaller than 1 NPLC giving lower resolution. No free lunch. It will be instructive to see the results.
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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #287 on: November 25, 2016, 02:33:23 PM »
I took my "heated" 2dw232 and breadboarded it into the following circuit, just using cheap resistors.  The objective was to see if it would start, and to tweak the heater parameters. the 4.4mA zener current put the 0TC point of the zener is at a good place to heat the zener to.

It does start. The integrator gain was reduced 100x from the LTZ1000 circuit to get it to oscillate less. The result was much worse than I expected; almost 100ppm/C. 
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Offline Kleinstein

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #288 on: November 25, 2016, 09:37:33 PM »
At 4 mA the TC of the zener section alone should be rather high (and the zener + diode) is likely not yet really low.

Even with external temperature control one should start with an current that produces a rather low TC. The main thing the temperature control is effective with is avoiding the second order TC - here even a rough regulation helps a lot. So a reasonable aim would be more like a current set to have a linear TC somewhere in the < 10 ppm/C range and than have temperature control down to the 0.1 K range. It might be possible to use the oven (e.g. use modulated temperature for adjustment) also to do in circuit adjustment of the current to get the TC really down (e.g. < 1 ppm/K).

There is nothing special with the 50 C setting : the curve from the DS is just a typical one, with a lot of possible variations between samples (e.g. current to get a similar curve might be anywhere from about 3 mA to 20 mA, or at a 5 mA current the maximum in voltage could be at a totally different temperature. So even with temperature control one should have an individually set current.

If one only has cheap resistors available one should use the unscaled output from the reference, the scaled up version can be still Ok to set the current.

For temperature control the internal sensor is rather slow - thus not that much gain possible in a simple configuration. To get a really good regulation one might need a second, faster sensor. One could still use the ref. internal sensor for the integral part. So the internal sensor still sets the final temperature, but the external sensor allows faster settling and reaction.

Using a resistor as a heat has the difficulty that this is square law heater - this would need a rather conservative / slow loop tuning. It might be better to use a transistor as a heater as this allows an nearly linear heater response.
 
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Offline VintageNut

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Re: Ultra Low Noise Reference 2DW232, 2DW233, 2DW23x
« Reply #289 on: November 26, 2016, 02:48:09 AM »