Author Topic: Ultra Precision Reference LTZ1000  (Read 873444 times)

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Offline quarks

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Re: Ultra Precision Reference LTZ1000
« Reply #25 on: January 13, 2013, 05:54:32 pm »
http://www.pa4tim.nl/?p=3624. Prema 5017 7.5 digit benchmeter. Very solid build. The meter does not switch of totally uing the front powerbutton, the reference stays powered.

your website is just great I have walked through it several times already and always find new and interesting details.
Also the translation on the site works quite good for me.

Thx a lot

edit: I just saw this http://www.pa4tim.nl/?p=2733 so you are my man.
In another post I asked for infos/help https://www.eevblog.com/forum/reviews/esi-resitance-standard-sr1010-and-standard-resistor-sr104/msg171260/#msg171260 but unfortunately had no reply. And now I see you have the same Set ESI SR1010 (also the same values 10 Ohm to 100k).
« Last Edit: January 13, 2013, 06:17:36 pm by quarks »
 

Offline UPI

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Re: Ultra Precision Reference LTZ1000
« Reply #26 on: January 13, 2013, 05:59:24 pm »
Reminds me of this relatively quick/inexpensive idea:

http://www.romanblack.com/xoven.htm
 

Offline SeanB

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Re: Ultra Precision Reference LTZ1000
« Reply #27 on: January 13, 2013, 06:03:57 pm »
Not a vacuum, but in a sealed enclosure with a large sachet of silica gel inside to adsorb water. Heat it up in an oven to dry it out well and then place in the dry enclosure hot and then seal it up while it is still hot. Then it will make a very low humidity interior. you will need to have IP68 rated connectors in the box, and preferably a smaller inner box to hold the reference in an insulated place. You can have heaters in the outer box to keep it at a stable temperature, and this will keep the inner stable. All you need on the outer is to keep it to within 2C, as the inner insulation will attenuate the variances. I have seen this ( without the dessicant) in an appnote to get a inner box to be temperature stable to within millidegrees.
 

Offline chrome

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Re: Ultra Precision Reference LTZ1000
« Reply #28 on: January 13, 2013, 06:08:32 pm »
Can anyone tell my why 6.95V?

It seems like such an arbitrary value.

I'm sort of assuming it's inherit with the design maybe?
 

Offline SeanB

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Re: Ultra Precision Reference LTZ1000
« Reply #29 on: January 13, 2013, 06:11:58 pm »
Reminds me of this relatively quick/inexpensive idea:

http://www.romanblack.com/xoven.htm

I did that years ago, and they work well.

6.95V as it is a stable point where the voltage is not quite avalance breakdown and not quite zener action. Lower and higher voltages have drift with temperature, this is a sweet spot in the characteristic. Often you get a 6V2 zener diode internally in series with a silicon diode to make a 6V8 unit, as this is also very stable as the tempco's of the zener and the diode are nearly the same but of opposite direction so they cancel out nearly totally.
 

Offline (In)Sanity

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Re: Ultra Precision Reference LTZ1000
« Reply #30 on: January 13, 2013, 06:20:15 pm »
Thanks for the replies about the vacuum,  Potting I assume would be subject to moisture absorption and too slow to respond to temperature changes or corrections ?  So if it got cold for example it would take far to long to stabilize and perhaps have too much hysteresis?

Also which would be better for a 10.0000 volt reference,   a 6.95 and an op-amp or two 6.95's and a voltage divider ?   Which would be more stable ?

I'm full of questions at the moment.

Thanks,

Jeff
 

Offline SeanB

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Re: Ultra Precision Reference LTZ1000
« Reply #31 on: January 13, 2013, 06:34:37 pm »
Potting would also stress the references. the biggesst issue is the resistors you use, not the opamp. You can get an opamp that is chopper stabilised, which removes it's own drift, but the resistor drift determines the stability. Better to use a single reference and multiply it up to 10V, one less source of error.
 

Offline (In)Sanity

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Re: Ultra Precision Reference LTZ1000
« Reply #32 on: January 13, 2013, 06:53:08 pm »
Potting would also stress the references. the biggesst issue is the resistors you use, not the opamp. You can get an opamp that is chopper stabilised, which removes it's own drift, but the resistor drift determines the stability. Better to use a single reference and multiply it up to 10V, one less source of error.

Thanks Sean,   that's what I was wondering.   I was looking to see which would be the lesser of the two evils.  To build one of these references correctly appears to be a very expensive endeavor with $90 references, $28 resistors and an equally expensive trim pot which should be avoided if possible,  ohh and let's not forget the chopper amp.   I may still pick up an LM399 just for experimentation sake and not breaking the bank.  I'm fortunate that I have a full finished basement and the temperature down here stays pretty constant relative to the rest of the house. So my 3457A also stays pretty stable.  I'm pretty good with long term projects,  so this could be fun.

Jeff
 

Offline SeanB

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Re: Ultra Precision Reference LTZ1000
« Reply #33 on: January 13, 2013, 07:04:24 pm »
Often the resistors are selected to be close, then a variable is used to get the final adjustment and is replaced by a fixed value. Leads to using Vishay foil on glass resistors in series and with final trim being by soldering a few low TC metal film resistors and then cutting resistor leads to trim up to the right value.
 

Offline PA4TIM

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Re: Ultra Precision Reference LTZ1000
« Reply #34 on: January 13, 2013, 07:11:14 pm »
http://www.pa4tim.nl/?p=2531 my LM399 ( the last one at the bottom, all my reference projecs are on this page)

Quarks: i have the ESIs but I did no stability tests with them. If i use them to calibrate I measure all off thecterminals and then take the avarage. Then measure all in serie and that must be the same value as the 12 separate. I have the bar that sets them parallel and I'm told this is enhances the precision by averaging out the differences.

Mine all measure very constant. No significant differences between terminals of one unit.
Problem of monitoring drift, tempco ect ( Vrefs, resistors, capacitors ect) is you never know what is drifting, the DUT or the instrument or both  :)

Is it because australia is very far away or is it just me. This forum is very slow, it takes ages for pages to open, before I can type comments and many notifications never seem to arrive. ( do I made wrong settings 's ? )
It would be great is i could set notifications on permanent z
www.pa4tim.nl my collection measurement gear and experiments Also lots of info about network analyse
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Offline SeanB

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Re: Ultra Precision Reference LTZ1000
« Reply #35 on: January 13, 2013, 07:15:14 pm »
Server is in the USA. They must be awake and watching movies............
 

Offline (In)Sanity

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Re: Ultra Precision Reference LTZ1000
« Reply #36 on: January 13, 2013, 07:55:27 pm »
Server is in the USA. They must be awake and watching movies............

Haaa,  the only movies I watch are electronics related for the most part.  Sadly I can't stream anything in HD anymore,  even though I have a 20 Meg connection.  Everything is going to crap lately..but that's another topic.

Thanks for the information about not using a trim pot.  I kind of knew that in the back of my head,  but somehow was in denial about it actually being done that way.   I wonder if anyone has made any good references by balancing out the positive and negative temperature coefficients of the devices in the circuit?   I know most DMM's and such have a thermistor or ten to obtain somewhat of this behavior.  I guess it would be no better then just using an oven no matter which way you rolled it.   Perhaps a combination of the methods.   I'm such a newb at temperature stability issues.   

Also can't everything be corrected in software :)

Jeff
 

Offline quarks

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Re: Ultra Precision Reference LTZ1000
« Reply #37 on: January 13, 2013, 08:14:50 pm »
http://www.pa4tim.nl/?p=2531 my LM399 ( the last one at the bottom, all my reference projecs are on this page)

Quarks: i have the ESIs but I did no stability tests with them. If i use them to calibrate I measure all off thecterminals and then take the avarage. Then measure all in serie and that must be the same value as the 12 separate. I have the bar that sets them parallel and I'm told this is enhances the precision by averaging out the differences.

Mine all measure very constant. No significant differences between terminals of one unit.
Problem of monitoring drift, tempco ect ( Vrefs, resistors, capacitors ect) is you never know what is drifting, the DUT or the instrument or both  :)
Thx again,
I do also have  the optional parallel, serial-parallel compensation networks and the shorting bars and have measured allmost all possible  combinations.
What I am still interested in, is how resistance transfer works. If you could share some knowledge that would be great. But this is OT here  and I can, if there is any interest, update the other post with more details.
Tomorrow I will also pick up some more related ESI gear from custom.
« Last Edit: January 14, 2013, 10:05:05 am by quarks »
 

Offline Conrad Hoffman

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Re: Ultra Precision Reference LTZ1000
« Reply #38 on: January 15, 2013, 06:02:34 pm »
FWIW, my Analogic 8200 6 1/2 digit voltage/current reference uses the LM399 and it's remarkably good. If you can find the circuit on-line, it uses analog switches to change the output from a master divider chain and is definitely worth studying.
 

Offline quarks

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Re: Ultra Precision Reference LTZ1000
« Reply #39 on: January 15, 2013, 06:31:41 pm »
Hello Conrad,
analog switching sounds interesting and with LM199/299/399 I remember a Bop Pease article where he used multiple of them together. I will definitely try to have a look at it.

A first quick search for a Analogic 8200 schematic unfortunately showed no result for manual and service manual.
But the search lead to
https://www.eevblog.com/forum/projects/kelvin-varley-divider-(and-precision-voltage-source)/msg71081/?PHPSESSID=c8a26b98cc233fa3e62a0ec3c9f47bb1#msg71081
so I tried also Data Precision also with no luck. Do you maybe have a link or can post a photo/scan?

thx
quarks
 

Offline muvideo

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Re: Ultra Precision Reference LTZ1000
« Reply #40 on: January 15, 2013, 06:46:38 pm »
quarks:
http://www.ko4bb.com/Manuals/09%29_Misc_Test_Equipment/DataPrecision_8200_6.5_Digit_Calibrator_Service_Manual.pdf

I'm reading it now, it's a wonderful manual, almost an application note :)
Fabio Eboli.
 

Offline robrenz

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Re: Ultra Precision Reference LTZ1000
« Reply #41 on: January 15, 2013, 06:46:48 pm »
I believe this is it

Edit: Sorry muvideo I was too slow
« Last Edit: January 15, 2013, 06:48:31 pm by robrenz »
 

Offline quarks

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Re: Ultra Precision Reference LTZ1000
« Reply #42 on: January 15, 2013, 06:58:05 pm »
great, thx a lot
 

Offline quarks

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Re: Ultra Precision Reference LTZ1000
« Reply #43 on: January 17, 2013, 01:40:36 pm »
in the Wavetek 1271 I just saw, they use a LM399 and a LTZ1000 Board
 

Online Mechatrommer

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Re: Ultra Precision Reference LTZ1000
« Reply #44 on: January 17, 2013, 02:06:43 pm »
$40 a pop hmmm...
thx for the link. Have you tried this source? My feeling is unless one can confirm it is no fake I tend to stay away.
yup if you cant trust it then be pleased to stay away. i havent tried it myself and perharps wont be in near future. verifying ultra ultra thing is not easy. imagine you have 6.95V very stable nvm verification. and then what? reducing it to useful value using a divider? the resistors must be equally good. and then what? ADC? DAC? etc, as some people already highlighted it, all of them must be equally good. so you add up the cost to what? nvm the cost of time and pcb prototype. i'm not trying to kill some hope here but, analog is a kick arse thing its not suitable for a person esp like me (i'm thinking of regretting it :(), $40 is expensive already for me there must be reasons why those high end stuff cost multi $K. i believe i have no point here, just talking. but the most important part is... YMMV.
« Last Edit: January 17, 2013, 02:12:44 pm by Mechatrommer »
if something can select, how cant it be intelligent? if something is intelligent, how cant it exist?
 

Offline free_electron

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Re: Ultra Precision Reference LTZ1000
« Reply #45 on: January 17, 2013, 03:11:39 pm »
I believe bob pease had a circuit using a few lm399s to make a nanovolt reference.
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Offline PA4TIM

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Re: Ultra Precision Reference LTZ1000
« Reply #46 on: January 17, 2013, 05:01:32 pm »
The Czar of bandgap references himself, that must be a decent design.
Do you know where it was publiced ?
www.pa4tim.nl my collection measurement gear and experiments Also lots of info about network analyse
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Offline muvideo

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Re: Ultra Precision Reference LTZ1000
« Reply #47 on: January 17, 2013, 05:35:05 pm »
I remember only one of his "What’s All This ___ Stuff, Anyhow?" series,
this one: http://electronicdesign.com/archive/what-s-all-long-term-stability-stuff-anyhow
But I'd like to know if there is some more in-depth article...

Fabio.
Fabio Eboli.
 

Offline free_electron

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Re: Ultra Precision Reference LTZ1000
« Reply #48 on: January 17, 2013, 06:34:08 pm »
i think it's in one of his Bob Pease Show video's... hang on ...



or it may be in his book analog troubleshooting. he uses like 10 of em ...
« Last Edit: January 17, 2013, 06:42:05 pm by free_electron »
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Offline jnd

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Re: Ultra Precision Reference LTZ1000
« Reply #49 on: January 18, 2013, 12:16:41 am »
i think it's in one of his Bob Pease Show video's... hang on ...



or it may be in his book analog troubleshooting. he uses like 10 of em ...
I saw this one just week or two ago, there is one LM399. BTW TI's channel on Youtube have them reuploaded in better quality (I tried to search there for "anyhow") which is interesting. The new version is here, it's still pretty relevant to the precision talk here:
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