Author Topic: Are cheap AD584 units worth it?  (Read 63163 times)

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Offline leonerdTopic starter

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Are cheap AD584 units worth it?
« on: March 18, 2016, 12:04:48 pm »
I see you can get an AD584 built up in a nice case all ready for use, for peanuts cost these days. Eg.

  http://www.ebay.co.uk/itm/KKMOON-High-Precision-Voltage-Reference-Module-AD584kH-Single-button-Operation/381300503613

The AD584 offers 15ppm/degC, which I'm quite sure is adequate for my needs. But are these units actually worth it though, or would I be better off paying a little more for something nicer?

One concern I have with this unit is that it has outputs at 5V, 7.5V and 10V, yet the power input to the unit is only 5V. So to generate those voltages it's going to have to boost it up somehow. Looking carefully at the board, I believe I can see an inductor and a big diode in what looks like a classic boost-mode SMPS. Surely that's going to put out a lot of switching noise, if you want a stable voltage.

So would I be best to ignore these units and look for something that takes 12V in directly? Or maybe I could post-mod it, take out that switching unit and feed a stable (linear-regulated) 12V directly?
 

Offline acbern

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Re: Are cheap AD584 units worth it?
« Reply #1 on: March 18, 2016, 12:46:25 pm »
Depending on your expectations re. accuracy it may be enough. But keep in mind, this is a not temperature regulated device, with non-hermetic, not pre-aged components. You will have all kinds of drifts, easily a few 100ppm in a couple of months. You have (from what I can see), no traceable accuracy data of the device used to calibrate it. All, to be fair, not expectable at that price. So for a 3.5 or 4.5 digit DMM, it is probably enough.
 

Offline tszaboo

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Re: Are cheap AD584 units worth it?
« Reply #2 on: March 18, 2016, 01:47:35 pm »
They are selling it less than half the booking price of the reference itself?? Sure...
Anyway I dont think anything more than a 3-5 PPM/K reference voltage with pre-regulation is really worth it. I mean I have a REF5050A in an altoids box with a 9V battery, which was  run for a week, and plugged into a 3458A, that will be better than this.
I mean it is probably fine to calibrate a 8-10 bit ADC with its front end, but nothing more.
 

Offline mojoe

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Re: Are cheap AD584 units worth it?
« Reply #3 on: March 18, 2016, 06:00:49 pm »
I bought four of these just recently: http://www.ebay.com/itm/181863456673

These are the "L" version chip, which has better specs and is also hermetically sealed. It is no longer made. I suspect that these were salvaged from something, which may actually be a good thing. These are probably well aged. You don't get that funky 15V battery that is in the picture.

According to the spec sheet, you should power this chip with at least 15 V, although it will work at lower voltage. You have to look around for an older specsheet, as the new one doesn't list the "L" version.

I currently have the third of the four I bought hooked up to a bench supply and my HP 3457A. I let each one cook for a few days and monitor the voltage output at 10 V. The first two were better than spec and pretty stable.

One thing I noticed about the three tested so far is that the first 3-4 times you power it on, you get some random voltage that is lower than 10 V. I suspect that the chip is oscillating. I plan on checking this with a scope over the weekend. I noticed that there are more caps on these boards than the circuit in the specsheet. I understand that sometimes a capacitor on the output can make the chip oscillate. I haven't traced the circuit yet. Also slated to do over the weekend.

One amusing item - each board came with a small folded slip of paper with very precise voltages listed for each of the four output voltages. So, at first glance, it looks like someone went to the trouble to check each board. That's what you think. All four slips of paper had the exact same numbers printed on them. And of course, these numbers didn't match the actual output voltages. Sometimes I wonder, why do they bother with this type of deception, when it is so easy to disprove?
 

Offline Arhammon

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Re: Are cheap AD584 units worth it?
« Reply #4 on: March 19, 2016, 07:17:05 am »
I bought four of these just recently: http://www.ebay.com/itm/181863456673

One amusing item - each board came with a small folded slip of paper with very precise voltages listed for each of the four output voltages. So, at first glance, it looks like someone went to the trouble to check each board. That's what you think. All four slips of paper had the exact same numbers printed on them. And of course, these numbers didn't match the actual output voltages. Sometimes I wonder, why do they bother with this type of deception, when it is so easy to disprove?
I bought this board from this seller six months ago. This board hasn’t come with paper. The seller said he did not understand what a paper, I want from him.  Apparently, a lot of people asked for a refund and he had to print fake papers.
I’m feeling is better to buy the cheapest AD584KH, like this:
https://xdevs.com/review/ad584_vref_test/
 

Offline Andreas

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Re: Are cheap AD584 units worth it?
« Reply #5 on: March 19, 2016, 07:55:30 am »

These are the "L" version chip, which has better specs and is also hermetically sealed. It is no longer made. I suspect that these were salvaged from something, which may actually be a good thing. T
One amusing item - each board came with a small folded slip of paper with very precise voltages listed for each of the four output voltages. So, at first glance, it looks like someone went to the trouble to check each board. That's what you think. All four slips of paper had the exact same numbers printed on them. And of course, these numbers didn't match the actual output voltages. Sometimes I wonder, why do they bother with this type of deception, when it is so easy to disprove?

Hello,

up to now my opinion on these devices was:
You get at least some measurement values which are from a calibrated instrument.

Although for a bandgap reference you can usually expect drifts from 100-200uV over several months.

Lets summarize:
- in every case you get re-stamped devices
  (the sample of AD that I bought from local distributor has laser engravement and the PIN1 marker on bottom side of the marking)
  so it is easy to change a JH device to a LH device.

- you do not get necessarily measurement values of your device which would be valid at least some weeks.

So the worth of all is not more than the parts price.

With best regards

Andreas
 

Offline acbern

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Re: Are cheap AD584 units worth it?
« Reply #6 on: March 19, 2016, 08:35:35 am »
I would not even bet these are not faked parts. The Fluke ref. and others have been faked as we have read here.
 

Offline Muttley Snickers

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Re: Are cheap AD584 units worth it?
« Reply #7 on: March 19, 2016, 09:32:50 am »
I've also been looking into these modules, it seems that the AD584LH is still readily available on some of the cheaper basic yellow PCB modules on Ebay, most of the acrylic cased units that I have seen now have the AD584KH onboard unless you are willing to pay almost double the price for one with the AD584LH and then there is no guarantee as to what you are getting or how good a reference they really are.

Anyway Scullcom does an excellent video and comparison of a few units, certainly worth a look if you are interested.

   
 
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Offline mojoe

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Re: Are cheap AD584 units worth it?
« Reply #8 on: March 19, 2016, 09:27:51 pm »
Looking at what I received, I don't think that these parts have been faked or re-labeled. They certainly look like they have been used before. In any case, in the short term (two days each), all four of mine exceed the voltage tolerance spec for the "L" part.

From the specsheet (only tested at 10 V so far):

Maximum Error for Nominal Outputs of: 10.000 V     AD584J = +/- 30 mV     AD584K = +/- 10 mV     AD584L = +/- 5 mV

The worst one of the four was 3.5 mV high. All four have been high.

The last one that I still have hooked up is only fluctuating about +/- 40 uV and that could be induced noise on my test leads. I need to make some shielded test leads.

These certainly aren't a high precision voltage reference, but should be good enough for checking the average hobbyist handheld DMM. I bought four of these because they were so inexpensive and to satisfy my curiosity. I don't need them, as I have a much higher precision and more versatile voltage reference that is currently out for calibration.

 
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Offline mojoe

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Re: Are cheap AD584 units worth it?
« Reply #9 on: March 19, 2016, 09:31:26 pm »
Anyway Scullcom does an excellent video and comparison of a few units, certainly worth a look if you are interested.

Yes, I watched that a few nights ago. The first one is essentially the same as what I linked to. The last one was heavily discussed here some time ago. A grossly overpriced unit made by someone who thinks he has some secret knowledge that makes his POS better than it should be (IMO). If he is reading this and takes offense to my OPINION, suck it up. I won't get into an argument with you. And please don't quote the bible at me.
« Last Edit: March 20, 2016, 02:54:26 am by mojoe »
 

Offline hydrogen maser

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Re: Are cheap AD584 units worth it?
« Reply #10 on: March 19, 2016, 10:46:30 pm »
I have one of these and it looks exactly what the OP linked to. How good is it? No idea, I bought it because it was cheap and looked interesting. Mine has a sticker on the back that says "Hp 3458A" and then lists what was "measured" for each voltage setting. The number next to each voltage is in ink pen and goes out to 5 decimal places. Would I trust this thing for anything critical? Nope but it is OK to see if a multi-meter is way off.
 

Offline mojoe

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Re: Are cheap AD584 units worth it?
« Reply #11 on: March 20, 2016, 02:53:23 am »
Just curious, what numbers did you get on that slip of paper? Here is what I got (printed) with all four.

2.5V     2.49942V
5V     5.00037V
7.5V     7.50042V
10V     10.00066V

Same meter, temperature and date on all four. Just amazing how all four of them put out the exact same voltages  :-DD
 

Offline hydrogen maser

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Re: Are cheap AD584 units worth it?
« Reply #12 on: March 20, 2016, 03:09:49 am »
Sticky label on the back written in ink pen:

2.5v: 2.49994
5.0v: 4.99888
7.5v: 7.49776
 10v: 9.99581
 

Offline mij59

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Re: Are cheap AD584 units worth it?
« Reply #13 on: March 20, 2016, 11:35:42 am »
In 2014 I bought the acrylic case version.

Printed sticker  on the back,  year 2014,  temperature 21 C, using a Agilent 34401A, with  written measurements.

Done some measurements with the KS 34465A and the Fluke 8846A, both units powered up for at least 1 hour, voltage reference was powered up for 1/2 hour before taken the measurements, ambient temperature 21,1 C according to the Fluke 87V  with thermocouple temperature probe.   

range   on sticker     KS 34465A   Fluke 8846A

2.5V     2.50070       2.50068          2.50070
5.0V     5.00035       5.00035          5.00037
7.5V     7.50418       7.50418          7.50421
10.0V  10.00285     10.00286        10.00292

KS 34465A bought in 2014, Fluke 8846A last calibration date 2008

 
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Offline tszaboo

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Re: Are cheap AD584 units worth it?
« Reply #14 on: March 21, 2016, 08:47:10 am »
Same meter, temperature and date on all four. Just amazing how all four of them put out the exact same voltages  :-DD
Well that preatty much sums up what I think about these references. One should know that calibration is some degree trust and some degree technical aspect.
How much do you trust a random chinese ebay seller? (with free shipping, sells like hot cookies)
 
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Offline Muttley Snickers

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Re: Are cheap AD584 units worth it?
« Reply #15 on: April 14, 2016, 04:19:49 am »
I've been meaning to order a couple of these modules for a few weeks and today bit the bullet on one of each, so I should end up with both a AD584LH and AD584KH reference to have a play around with.

I did PM another member for a link to the Ebay site where they got theirs from but that particular seller was not listed with Ebay AU so I simply chose a couple of random sellers that had the most colourful negative feedback, a bit of a worry really.
 

Offline tronde

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Re: Are cheap AD584 units worth it?
« Reply #16 on: April 17, 2016, 06:21:52 pm »
Just curious, what numbers did you get on that slip of paper? Here is what I got (printed) with all four.

2.5V     2.49942V
5V     5.00037V
7.5V     7.50042V
10V     10.00066V

Same meter, temperature and date on all four. Just amazing how all four of them put out the exact same voltages  :-DD


You are not alone... ;D
 

Offline Harfner

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Re: Are cheap AD584 units worth it?
« Reply #17 on: April 18, 2016, 03:51:19 pm »
I bought the acrylic version in March 2015 from seller diyelecmall108. It has a sticker on the back, date 2015, temp 21°C, voltages are written by hand.

 2.5V     2.5077
 5.0V     5.00147
 7.5V     7.50841
10.0V  10.00472

On arrival, I checked the 10V against another 10V standard and found it within spec of the multimeter.

I bought the LH version shown by Muttley Snickers from 2012moon816 in June 2015. It has a printed sheet dated 2015-6-23 looking very similar to one shown by tronde.
 2.5V     2.500,21
 5.0V     4.999,20
 7.5V     7.500,01
10.0V    9.998,19
« Last Edit: April 18, 2016, 03:55:02 pm by Harfner »
 

Offline Mark Hennessy

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Re: Are cheap AD584 units worth it?
« Reply #18 on: April 18, 2016, 10:13:54 pm »
I recently bought a number of these, and have written about them (including schematics and measurements) here: http://www.markhennessy.co.uk/ad584_references/

The ICs are reclaimed, and therefore nicely aged (hopefully!).

The KKMOON version is good, and comes with believable calibration data. Some switching noise. There is a battery management IC controlling a dual MOS-FET, but a pair of deliberate solder blobs are shorting out the MOS-FETs (same on others that I've seen using the "2015" PCB).

My "L" version also came with the same fake cal certificate. Glad to see a decent number of folks on here have exactly the same numbers I do - along with a couple of other people from another forum. What date codes do you all have on the IC? In all the close-up photos I've seen, I've only ever seen "1015". Could they be re-printing (hence not genuinely "L"-spec), or did they simply stumble across a massive batch somewhere? The ICs are clean and shiny, so perhaps could be NOS rather than reclaimed.

Finally, I picked up a tiny bare-bones PCB unit that uses the "J"-spec IC (though it comfortably meets "L"-spec if my measurements are reliable). Useful for building into a project.

All units meet their spec, and are great for the money.

The start-up problem is caused by the capacitor surrounding the IC (pins 6 and 7). There's no external sign of oscillation that I could find when investigating. Reduce it to 10n to reduce the time spent in limbo. For testing, set the output to 10V (remove jumpers), and then briefly short the 2.5V pins - that reliably provokes it. I haven't noticed this behaviour with the KKMOON unit.
 

Offline Muttley Snickers

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Re: Are cheap AD584 units worth it?
« Reply #19 on: April 18, 2016, 10:20:13 pm »
Thanks Harfner for the reference figures and welcome to the forum..... :-+

I'm not expecting too much out of these modules and will probably be lucky if they even turn up, if they arrive then I will conduct some tests over time and post my findings, occasionally I see test equipment for sale locally and just want a small reliable reference that hopefully will give me a guide.   

Many thanks..... :)



 

Offline Muttley Snickers

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Re: Are cheap AD584 units worth it?
« Reply #20 on: April 18, 2016, 11:07:36 pm »
I recently bought a number of these, and have written about them (including schematics and measurements) here: http://www.markhennessy.co.uk/ad584_references/

Wow, Mark that really is the benchmark guide to all of these modules and a brilliant well documented piece, I have printed the entire page and saved all of the associated links, thank you sir very much...... :-+
 

Offline dannyf

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Re: Are cheap AD584 units worth it?
« Reply #21 on: April 19, 2016, 01:01:47 am »
Quote
Scullcom does an excellent video and comparison of a few units,

He got his for 9 pounds, right?

Mine produced the following measurements:

Quote
13.0 - 36v, 12.3882v

11.0 - 32v,  9.9011v

 8.0 - 28v,  7.4251v

 6.0 - 26v,  4.9524v

 3.3 - 24v,  2.4732v
=========    =======
  Vin --GND-- Vout

However, I only spent a few cents on some TL431A, :), in serial and with 1K resistors.

Not bad, right?
================================
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Offline zlymex

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Re: Are cheap AD584 units worth it?
« Reply #22 on: April 19, 2016, 06:26:48 am »
I recently bought a number of these, and have written about them (including schematics and measurements) here: http://www.markhennessy.co.uk/ad584_references/

The ICs are reclaimed, and therefore nicely aged (hopefully!).
...............
Very nice review.
Yes, there are many reclaimed IC in China market, and pretended to be new. There are groups of people specializing in doing so including re-tin, re-print and even leads extension for metal can. When I buy ICs here, I either choose from a reputable market with high price(but genuine) or reclaimed with original leads and original marking. I'm now in possession  of more than 50 reclaimed LTZ1000, all tested good.
 

Offline Kjelt

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Re: Are cheap AD584 units worth it?
« Reply #23 on: April 19, 2016, 07:02:35 am »
I recently bought a number of these, and have written about them (including schematics and measurements) here: http://www.markhennessy.co.uk/ad584_references/ 
Thanks! I ordered the KKMoon (#1) today and another cheaper one (#2) with the better L version, going to swap them and keep the kkmoon with a l version, lets see what we get.
 

Offline Mark Hennessy

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Re: Are cheap AD584 units worth it?
« Reply #24 on: April 19, 2016, 09:42:43 am »
Thank you all for the positive feedback  :-+

And thanks to zlymex for the insights to the Chinese market place. And I can't wait to see how you will use all those LTZ1000s - you could build the ultimate statistical reference with those  :-DD

I've got a couple more articles like that in preparation - just waiting on eBay deliveries :)
 

Offline zlymex

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Re: Are cheap AD584 units worth it?
« Reply #25 on: April 19, 2016, 12:27:23 pm »
- you could build the ultimate statistical reference with those  :-DD
I certainly could, with total of more than 100 LTZ1000(plus 40+ brand new).  The rough plan is ten times ten.
 

Offline bitseeker

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Re: Are cheap AD584 units worth it?
« Reply #26 on: April 19, 2016, 09:18:38 pm »
I'm now in possession  of more than 50 reclaimed LTZ1000, all tested good.

Wow, zlymex. Are you building references for us? :-DMM
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Offline zlymex

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Re: Are cheap AD584 units worth it?
« Reply #27 on: April 20, 2016, 01:32:22 am »
I'm now in possession  of more than 50 reclaimed LTZ1000, all tested good.

Wow, zlymex. Are you building references for us? :-DMM
Well, building 100+ refs all in their own box is a hell of a work for me.
The original idea was to build a super statistical one. My current plans is two level statistical with just only 11 boxes.
 

Offline Theboel

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Re: Are cheap AD584 units worth it?
« Reply #28 on: April 20, 2016, 01:51:28 pm »
Someone is very serious about precision  :-+
 

Offline bitseeker

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Re: Are cheap AD584 units worth it?
« Reply #29 on: April 20, 2016, 06:01:37 pm »
The original idea was to build a super statistical one. My current plans is two level statistical with just only 11 boxes.

That sounds very cool. I'm looking forward to your thread on it.
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Offline Andreas

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Re: Are cheap AD584 units worth it?
« Reply #30 on: April 20, 2016, 08:27:37 pm »
I recently bought a number of these, and have written about them (including schematics and measurements) here: http://www.markhennessy.co.uk/ad584_references/

Hello,

thanks for the article.

some annotations:
You are in doubt wether the plastic case is equal in specs to the Metal CAN housing.
Usually it is not. With a plastic package you can measure up to 15 ppm output voltage change
 for humidity changes between 40 to 70% rh. (Depending on device).

And usually the (best) ageing spec is only for hermetically sealed device.
In most datasheets this is mentioned partly as a footnote.
Even if the hermetically device is already obsolete: see LT1027, REF102.
For the AD584 the footnote is not there (because this fact is evident or does it really play no role?)

The AD584 has a relative large input voltage dependency. (20-50 ppm/V)
So if you use a battery (non stabilized) you should not only record the temperature but also the supply voltage.

The microprocessor could be a Holtek HT68F002  (best guess).
There are not many processors with supply on pin 1 + 8.
(and since pin 4 is a output the pic12F508/627/683 devices do not fit)

With best regards

Andreas
 

Offline Mark Hennessy

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Re: Are cheap AD584 units worth it?
« Reply #31 on: April 20, 2016, 09:37:42 pm »
Hi Andreas,

Thanks for the feedback - you raise some good points :)


You are in doubt wether the plastic case is equal in specs to the Metal CAN housing.
Usually it is not. With a plastic package you can measure up to 15 ppm output voltage change
 for humidity changes between 40 to 70% rh. (Depending on device).

And usually the (best) ageing spec is only for hermetically sealed device.
In most datasheets this is mentioned partly as a footnote.
Even if the hermetically device is already obsolete: see LT1027, REF102.
For the AD584 the footnote is not there (because this fact is evident or does it really play no role?)

Yes, I'm certainly aware that humidity can play a part with plastic cases. And because I live in an old house (where the workshop is in the cellar), I've had to learn a lot about the subject - and invest in a dehumidifier ;)

However, unless I've missed it, the datasheet doesn't differentiate between "H" and "N" in any parameter - as a result, I thought it was safest to not to speculate about it here.



The AD584 has a relative large input voltage dependency. (20-50 ppm/V)
So if you use a battery (non stabilized) you should not only record the temperature but also the supply voltage.

I did quote it (15.00V).

I agree that the line regulation is specified at 20-50ppm worst-case, but I found it was somewhat better than that. Admittedly, I didn't test it exhaustively, and in fact I think I only checked the 2nd unit, but I will double-check this aspect soon.

In the meantime, here's what I recorded here: http://www.markhennessy.co.uk/ad584_references/#unit2_summary

A 5.5V drop in supply voltage (18 to 12.5V) caused a 200uV change in the 10V output voltage, which is 20ppm overall, or 3.6ppm/V. Surprisingly good.


The microprocessor could be a Holtek HT68F002  (best guess).
There are not many processors with supply on pin 1 + 8.
(and since pin 4 is a output the pic12F508/627/683 devices do not fit)

Thanks - that's useful insight :-+

BTW, I'm playing around with an AD588 at the moment :-DMM

All the best,

Mark
 

Offline zlymex

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Re: Are cheap AD584 units worth it?
« Reply #32 on: April 21, 2016, 12:53:47 am »
BTW, I'm playing around with an AD588 at the moment :-DMM
I have two AD588 but I don't like them at all. The spec for noise and drift is just average, it need dual supply and draw too much current which means the self-heat will add thermal related problems such as EMF and low frequency noise.
 

Offline Mark Hennessy

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Re: Are cheap AD584 units worth it?
« Reply #33 on: April 21, 2016, 12:46:15 pm »
BTW, I'm playing around with an AD588 at the moment :-DMM
I have two AD588 but I don't like them at all. The spec for noise and drift is just average, it need dual supply and draw too much current which means the self-heat will add thermal related problems such as EMF and low frequency noise.

This is part of my survey of cheap Chinese voltage references - I have one from KKMOON which seems quite nice so far, and am awaiting delivery of another type. Links here:

http://www.ebay.co.uk/itm/172024077034
http://www.ebay.co.uk/itm/171927104601

As before, I'll put up some photos, schematics, basic measurements, etc.

I'm not chasing the ultimate reference here - that's another project :) - rather, this investigation started as a result of a forum conversation elsewhere. Most people who were interested in these eBay units are using 3.5 or 4.5 digit meters, so for them, the AD584 modules are probably fine.

I haven't had a chance to fully study the AD588 datasheet yet, but it certainly seems like a nice step up from the AD584 in terms of basic initial accuracy and tempco. Line regulation looks worse at a glance. Yes, the power supply requirements seem like a PITA. But against that, the extra op-amps in there might be useful for making a precision current source or something similar - sort-of like a "super-LM10", if you see what I mean  :-+

Cheers,

Mark
 

Offline pelule

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Re: Are cheap AD584 units worth it?
« Reply #34 on: April 21, 2016, 06:42:24 pm »
Quote
@ mojoe
You don't get that funky 15V battery that is in the picture.
I regular order that 15V batteries in China since several year. Never had any issue yet.
http://www.aliexpress.com/item/free-ship-15v-10F20-primary-battery-dry-battery-multi-meter-heavy-duty-battery/923034386.html

PeLuLe
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Offline Andreas

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Re: Are cheap AD584 units worth it?
« Reply #35 on: April 21, 2016, 08:40:48 pm »

A 5.5V drop in supply voltage (18 to 12.5V) caused a 200uV change in the 10V output voltage, which is 20ppm overall, or 3.6ppm/V. Surprisingly good.


Hello,

for a volt-nut there are better references:
A LT1027CCN8-5 I have measured around 14uV (<3 ppm) over 8.5 - 15.5 V. (0.4 ppm/V)
(3-8 ppm/V in data sheet).

Other references like LT1236AILS8-5 are even better (around 0.5-1ppm over 8-15V).

But of course the measurements done are not the same as stated in the datasheet.
In the datasheet they use pulsed measurements with no self heating effects.
Whereas I use constant voltage over longer times. (reflecting more the reality).

With best regards

Andreas
 

Offline Muttley Snickers

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Re: Are cheap AD584 units worth it?
« Reply #36 on: April 29, 2016, 06:41:45 am »
My AD584KH unit arrived yesterday nicely packaged in bubble wrap and the first thing I did was to take a few measurements and document the readings, I then hooked the unit up to a power supply at 5 volts to see what the battery state was at and the initial current draw was around 300 mA which rapidly diminished over about ten minutes to not much at all.

I then opened the unit up to insert a clear insulating shim between the battery and the PCB as others have done and the battery in this particular one appears to be rather crappy and slightly swollen, the unit initially took quite a while to settle on a final value in all selections enough for me to have serious concerns about the product but I found after about five hours of continuous testing with various meters that the module now settles in only a few seconds and is relatively consistent.

The nominated values on the label appear to be correct and a few of the meters that I tested with were in agreement with the label, certainly well within the specifications of both the module and the meters used. I noticed when putting in the shim that there was a fair bit of flux residue on the board and opened the unit back up to clean it off and during the cleaning process the negative lead for the battery came away with not much effort at all.

I am now waiting on the AD584LH module to arrive and hope to be able to take both units up to a fellow members place to run these things on some better gear than I have here.

The Ebay seller I got the unit from.
http://www.ebay.com.au/itm/High-Precision-4-Channel-2-5V-7-5V-5V-10V-Voltage-Reference-Module-AD584KH-/181873998781

The website that is on the screen print.
https://shop58034511.world.taobao.com/
 

Offline Kjelt

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Re: Are cheap AD584 units worth it?
« Reply #37 on: April 29, 2016, 06:51:30 am »
My AD584KH unit arrived yesterday nicely packaged in bubble wrap and the first thing I did was to take a few measurements
Mine arrived also wednesday, unbelievable quick from china to europe within a week, but I think since it was a german package it got delivered from a european warehouse or so.
My seller on ebay was tomtop_sales.
I took some measurements and they were spoton. I do not recognize the unstable behavior mine was very stable but I did not charge the battery, could that have something to do with it?
Anyway thanks for the shim advice will do that this weekend.
 

Offline Muttley Snickers

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Re: Are cheap AD584 units worth it?
« Reply #38 on: April 29, 2016, 07:05:29 am »
No this unit was definitely unstable regardless of the charge state and was still drifting dramatically by tens of millivolts for about an hour with a stable 21 degrees, after a few power cycles the unit seemed to stabilise and is now pretty well consistent, I also hadn't heard of anyone else having this problem and intended to give it some time before contacting the seller, as it is I am very happy but again time will tell.

Also I forgot to mention that I added another piece of clear insulating sheet to the top of the board to stop inserted banana plugs shorting anything out which others previously mentioned, this is a good quick fix and saves modifying the output jacks.
« Last Edit: April 29, 2016, 08:07:43 am by Muttley Snickers »
 

Offline Kjelt

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Re: Are cheap AD584 units worth it?
« Reply #39 on: April 29, 2016, 08:48:57 am »
Ok so now I have seen that my benchmeters and multimeter are pretty much within hobbieist level of calibration, what are you all going to do with these things ?  :)
 
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Offline bitseeker

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Re: Are cheap AD584 units worth it?
« Reply #40 on: April 29, 2016, 04:49:46 pm »
Excellent question, Kjelt, and one that has kept me on the fence about getting devices like these or the more finished voltage/current standards. I suppose that if I had a lot of equipment and standards that spanned all the required ranges, I could have the standards calibrated and then calibrate everything else accordingly.
TEA is the way. | TEA Time channel
 

Offline Muttley Snickers

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Re: Are cheap AD584 units worth it?
« Reply #41 on: May 04, 2016, 06:37:04 am »
The AD584LH module that I ordered a few weeks ago arrived today and I was just about to complain to the seller in regards to the delay after receiving an item sent email weeks ago, anyway it was really poorly packaged and was not supplied with any documentation whatsoever yet the Ebay listing indicates that it would be supplied with values.

It was around eight bucks so I'm not going to whinge about it and just glad that it turned up at all, I will however notify the seller to amend the listing so others who may be reliant on these values aren't disappointed, the unit is currently on the bench being tested and so far it seems to work.



   
 

Offline Mark Hennessy

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Re: Are cheap AD584 units worth it?
« Reply #42 on: May 04, 2016, 07:43:00 am »
Perhaps he's decided to stop giving out the fake certificates? No certificate is better than a fictitious one. But yes, I agree the listing should be amended - as it stands, it's "not as described", and plenty of buyers would complain about that.

What's the date code on your IC?
 

Offline Muttley Snickers

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Re: Are cheap AD584 units worth it?
« Reply #43 on: May 04, 2016, 11:33:39 am »
The date code on this AD584LH module is 1015 and looks exactly like the one in the picture that I posted earlier in the thread, I am hopefully going  to have a play around with it tomorrow and look at getting rid of those jumper links which are a bit of a pain, perhaps a decent rotary switch and a proper box might be in order for the interim.
 

Offline guy48065

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Re: Are cheap AD584 units worth it?
« Reply #44 on: May 19, 2016, 05:14:58 pm »
What can be done to boost the current capability without sacrificing the excellent power and load regulation? I'd like to use mine as a precision 10V excitation source, with about 100mA output at a minimum. The AD584 is limited to 10mA.
 

Offline Kleinstein

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Re: Are cheap AD584 units worth it?
« Reply #45 on: May 19, 2016, 06:14:07 pm »
The AD584 does not have separate voltage drive and sense lines. So all one can do is adding an low offset amplifier. This could be something like an OP07 or similar with a transistor to do most of the power driving.
 
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Offline Andreas

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Re: Are cheap AD584 units worth it?
« Reply #46 on: May 19, 2016, 07:52:14 pm »
What can be done to boost the current capability without sacrificing the excellent power and load regulation?

Hello,

I do not find that 20-50ppm/mA are a excellent value (compared to the LT1027 with 3-10ppm/mA).

In AN86 from Linear Technology there is a cirquit with a LTC1152 + LT1010 as buffer which can deliver the 100mA.

with best regards

Andreas
 

Offline Mark Hennessy

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Re: Are cheap AD584 units worth it?
« Reply #47 on: May 19, 2016, 08:39:17 pm »
What can be done to boost the current capability without sacrificing the excellent power and load regulation?
I do not find that 20-50ppm/mA are a excellent value (compared to the LT1027 with 3-10ppm/mA).

But remember that it's all relative.

Compared to the alternatives at his disposal, and considering his needs, it might well be excellent. Certainly, most bench power supplies drift rather more - but they are perfectly fit for purpose...

Now that I've acquired a handful of these things and am wondering what to do with them, building a "precision" bench power supply around them is one option. It won't be as good as the LT1027, but it'll be better than the usual grade units. Although I'm thinking that I'd be better off using the AD588 (better specs than the AD584, and sense lines, of course). It might be as simple as adding pass transistors and making use of the internal op-amps - but I haven't given that serious thought yet.
 

Offline Kleinstein

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Re: Are cheap AD584 units worth it?
« Reply #48 on: May 20, 2016, 08:58:47 am »
For delivering more power an external power stage like that with a LTC1052 and LT1010 (or just an transistor) it not that bad. Especially with a AZ Op, it can very well compensate for load changes.
 

Offline Kjelt

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Re: Are cheap AD584 units worth it?
« Reply #49 on: May 20, 2016, 12:09:16 pm »
In the meanwhile I have received both AD584 units, the one in the plexiglass box a AD584K is marked with some kind of mill, datecode 9210 so week 10 1992 which seems legit.
The other one is the AD584L it looks brand new, the markings are lasered (you can see the individual dots under a microscope) and has a datecode 1015 so week 15 2010.
The big question is, did AD make these still in 2010 and were they indeed lasered or is the last one a fake chip? Anyone that can give a decisive answer on this one?
« Last Edit: May 20, 2016, 12:12:00 pm by Kjelt »
 

Offline Muttley Snickers

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Re: Are cheap AD584 units worth it?
« Reply #50 on: May 20, 2016, 01:08:15 pm »
I cant help you with the manufacture date but others will know, my question is were either unit supplied with reference figures and can they be counted upon, the AD584LH I received was not supplied with figures and I have been corresponding with the Ebay seller who was most apologetic and openly offered a full refund even though I did not ask for nor seek one.

This is no big deal really but for anyone else counting on those values being both supplied and accurate it might be of importance and as mentioned most people are sick to death of stuff that takes weeks to arrive only to turn up faulty or not as described, not all of us seek the bottom dollar just a fair and reasonable deal.


« Last Edit: May 21, 2016, 12:11:08 am by Muttley Snickers »
 

Offline Mark Hennessy

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Re: Are cheap AD584 units worth it?
« Reply #51 on: May 20, 2016, 01:22:00 pm »
The other one is the AD584L it looks brand new, the markings are lasered (you can see the individual dots under a microscope) and has a datecode 1015 so week 15 2010.
The big question is, did AD make these still in 2010 and were they indeed lasered or is the last one a fake chip? Anyone that can give a decisive answer on this one?

I don't know, but am watching this closely. An awful lot of these are exactly like your picture, including one of mine.

My one appears to meet the L spec, so if they are fakes, they're good  :)
 

Offline RobK_NL

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Re: Are cheap AD584 units worth it?
« Reply #52 on: May 20, 2016, 01:34:28 pm »
The datasheet Rev.C was issued in 2012 and one of the differences with Rev.B is that the "L" was deleted. So it could well be that it was still made in 2010.
Tell us what problem you want to solve, not what solution you're having problems with
 

Offline Kjelt

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Re: Are cheap AD584 units worth it?
« Reply #53 on: May 20, 2016, 01:38:00 pm »
my question is were either unit supplied with reference figures and can they be counted upon
The K version in the plexibox had a sticker with reference voltages which I could verify upto the first 4 digits after the , so pretty good AFAICT.
The L version had the already much mentioned standard leaflet with numbers that do not correspond to the unit so no good.
 

Offline guy48065

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Re: Are cheap AD584 units worth it?
« Reply #54 on: May 20, 2016, 01:41:26 pm »
I bought 2 of the L-version boards and am pleased with the performance.  Well within AD specs.  These have to be legit, IMO.

#1: 10.0V = 10.00274  7.5V = 7.49969  5.0V = 5.00269  2.5V = 2.49918
#2: 10.0V = 10.00158  7.5V = 7.49881  5.0V = 5.00162  2.5V = 2.49829

2ppm/V increase @ 10V with an increase in supply from 15.0 to 20V.
28ppm/mA decrease @ 10V with resistive load (tested with 10K, 5K & 2K).

All measurements taken with an in-cal 34401A (10V = 9.99999 on cert.), 6-digit Slow mode, after minimum 1 hour warm-up of everything.  I bagged the board and wrapped it in a couple shop towels to isolate it from HVAC and equipment fans.  I'm particularly impressed with the lack of drift over time for a $6.59 "plug & play" module!

Mine came with the same "bogus" cal sheetlet.  Does anyone here read chinese?  Maybe it states the figures are "typical" and not Actual. 
« Last Edit: May 20, 2016, 02:04:42 pm by guy48065 »
 
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Offline Kjelt

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Re: Are cheap AD584 units worth it?
« Reply #55 on: May 20, 2016, 01:55:24 pm »
So here are my measurements, however not as official as guy48065 has done with one hour warmin etc. just power up two Keithley 2000 not calibrated for at least 8 years but that's all I have here  :)
The K-unit figures are pretty spot on, the L-unit figures are fiction.
 
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Offline escape

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Re: Are cheap AD584 units worth it?
« Reply #56 on: February 24, 2017, 08:24:07 pm »
Sorry to revive an old thread, but it made more sense to me to just keep it in here.

Regarding the date codes, the code on the KKMOON board I bought from a seller on Amazon last month is 9107.  Is it possible it's this old?

BTW, it did come with hand printed values.  I don't have a way to verify these values though.

Mine came with a micro-USB charging port instead of the round port found on older models.






 

Offline Kjelt

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Re: Are cheap AD584 units worth it?
« Reply #57 on: February 24, 2017, 09:27:06 pm »
Regarding the date codes, the code on the KKMOON board I bought from a seller on Amazon last month is 9107.  Is it possible it's this old?
Yes those are recycled from old electronic garbage, the only way why they are real and this cheap.
 

Offline MacMeter

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Re: Are cheap AD584 units worth it?
« Reply #58 on: March 02, 2017, 01:58:53 am »
Sorry to revive an old thread, but it made more sense to me to just keep it in here.

Regarding the date codes, the code on the KKMOON board I bought from a seller on Amazon last month is 9107.  Is it possible it's this old?

BTW, it did come with hand printed values.  I don't have a way to verify these values though.

Mine came with a micro-USB charging port instead of the round port found on older models.







Can you link the EBay page you bought yours on? Thanks!
 

Offline innkeeper

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Re: Are cheap AD584 units worth it?
« Reply #59 on: March 10, 2017, 04:20:32 am »
kinda makes you wonder if the 2015 date is the calibration date of the agelint used and not the date they did the voltage check.
Hobbyist and a retired engineer and possibly a test equipment addict, though, searching for the equipment to test for that.
 

Offline escape

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Re: Are cheap AD584 units worth it?
« Reply #60 on: April 28, 2017, 02:06:43 pm »
Can you link the EBay page you bought yours on? Thanks!
Sorry for the late response.  I bought mine on Amazon, because I didn't feel like waiting for it to be shipped from China.

http://a.co/45CANQr

But it was cheaper back when I ordered it.
 
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Offline Muxr

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Re: Are cheap AD584 units worth it?
« Reply #61 on: June 05, 2017, 02:56:26 pm »
If you have a decent power supply handy I would save a few bucks and skip the KKmoon unit. KKmoon unit is built well and it's fairly convenient, however the boost converter does add noise.

I did a full day run with both the KKmoon AD584 and the one sold by Alice. Also worth noting KKmoon's battery lasts about a day and a half of full operation, before it needs to be recharged.

If you're just looking to check your 4.5 digit meter, you're probably fine either way though.

 
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Offline metrologist

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Re: Are cheap AD584 units worth it?
« Reply #62 on: June 05, 2017, 06:27:48 pm »
Super Dooper! I bought mine the other day from t-happy on ebay, same seller as mojoe's units.

I have no way to check it, unless I get someone to do it for me...
 

Offline mokeman3

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Re: Are cheap AD584 units worth it?
« Reply #63 on: June 18, 2017, 09:47:04 am »
I recently bought a number of these, and have written about them (including schematics and measurements) here: http://www.markhennessy.co.uk/ad584_references/ 
Thanks! I ordered the KKMoon (#1) today and another cheaper one (#2) with the better L version, going to swap them and keep the kkmoon with a l version, lets see what we get.
I got my KKmoon (#1) from tomtop_sales today too, but after learning about the (#2) with the better L version, I just bought one of those ones with the 15-volt battery cut out in the PCB, and thought about doing the same thing: putting the better L version device in the pelexi-case KKmoon box.

Q: did you do that with yours ?

The AD584 that is in my KKmoon, looks really beat up, and it doesn't have the official Analogue Devices "triangle" on it, and I can't make out the date code. Makes me wonder if it's a AD knock-off, and not the real thing.

But I don't know that China (or any other place) has the ability to make devices like this anyhow, do they ?

And it does seem to drift like a mo-fo. It seems to get in a mode where the output isn't right, and you have to turn it off, and back on again.

Mine has a micro USB, but the charging LED is orange, not blue. The battery is also quite a bit smaller than earlier unit's I've seen.

Question for you folks with in-cal Agilent 34401A's and the like: have you thought about offering a service to members here to check these things for us, and offering an "actual reading" slip (or sticker) ?  Might be a way to turn a fast buck, and help out some of the folks with less accurate meters.


 

Offline Muxr

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Re: Are cheap AD584 units worth it?
« Reply #64 on: June 18, 2017, 04:20:26 pm »
The AD584 that is in my KKmoon, looks really beat up, and it doesn't have the official Analogue Devices "triangle" on it, and I can't make out the date code. Makes me wonder if it's a AD knock-off, and not the real thing.
I have both versions of the KKmoon reference. The one with the logo and the one without. I have not found them to be different in TempCo and noise (haven't had them long enough to ascertain drift).
Question for you folks with in-cal Agilent 34401A's and the like: have you thought about offering a service to members here to check these things for us, and offering an "actual reading" slip (or sticker) ?  Might be a way to turn a fast buck, and help out some of the folks with less accurate meters.
You have multiple options here. We are currently trying a traveling reference concept in the https://www.eevblog.com/forum/metrology/usa-calibration-club/msg1209295/#msg1209295 USA callibration club. Once the reference makes the full trip, we can compare the readings (some folks have in-cal instruments). This will take awhile.

Your other option is ordering a reference from voltagestandard.com:
Quote
As a benefit to our customers, and to keep the cost of ownership as low as possible, recalibration is free for the first two years after purchase- just send it back to us and for USPS Priority return shipping please include $7.00 in stamps or US currency or PayPal payment to doug@voltagestandard.com.  After two years the calibration charge is $10.00 plus shipping.
http://www.voltagestandard.com/-.html
 

Offline mokeman3

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Re: Are cheap AD584 units worth it?
« Reply #65 on: June 19, 2017, 05:17:54 am »
Well I started reading the cal club thread with the Traveling Reference Concept, and didn't get all the way thru it, but I've sorta lost sight of the goal of it.

And I have been in touch with Doug at voltagestandard.com.  What I was really after was his "DMMCheck" product, but he disco'd it. I really wanted one, and was after the current, and resistance standard that he offered.

But I fell prey to this guy's video starting at minute marker 20:00, and his findings:

But I should have just gotten the 'pentaref' instead of the KKmoon, - and I may still do that.
The guy isn't even that far from me, - he's in the State of Washington too, about 1.5 hours South of here.

Oh well, live and learn.

As far as the KKmoon, the output seems to be "porpoising" some (at least on the 5-volt range), and I can see the segments on the end of the bar graph on the Fluke 89 IV flashing back and forth, and that doesn't seem right (nor that noise).

I think I'm going to dig into it to isolate the switching power supply, and just power the can directly with ~15 (proly 18) volts of pure (battery) DC to see if any of that goes away.
 

Offline alm

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Re: Are cheap AD584 units worth it?
« Reply #66 on: June 19, 2017, 05:51:26 am »
Your other option is ordering a reference from voltagestandard.com:
[...]

Unfortunately Doug no longer ships his products outside the US:
Quote
Please note that we no longer ship to international destinations- only orders that are shipped to addresses within the USA are accepted.

So as far as affordable readily available voltage standards with something resembling calibration, the AD584 units appear to be the only game in town now for people living outside the US. Except for our +/- 2 ppm with shoddy soldering on a protoboard friend :P.

Offline Muxr

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Re: Are cheap AD584 units worth it?
« Reply #67 on: June 19, 2017, 06:08:12 am »
Your other option is ordering a reference from voltagestandard.com:
[...]

Unfortunately Doug no longer ships his products outside the US:
Quote
Please note that we no longer ship to international destinations- only orders that are shipped to addresses within the USA are accepted.

So as far as affordable readily available voltage standards with something resembling calibration, the AD584 units appear to be the only game in town now for people living outside the US. Except for our +/- 2 ppm with shoddy soldering on a protoboard friend :P.
Didn't realize about shipment outside of US. Bummer.

There is also this AD588 board.. http://www.ebay.com/itm/111840217453?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

It appears to have better tempco than the best AD584 reference I have.

I am getting a bit of popcorn noise with it, but it's not bad at all, there is also less noise. The only thing is, it requires both a +17V and a -17V +15V and a -15V rail.

« Last Edit: June 20, 2017, 03:35:01 pm by Muxr »
 

Offline alm

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Re: Are cheap AD584 units worth it?
« Reply #68 on: June 19, 2017, 02:26:31 pm »
Thanks for posting those measurements! At least your 588 sample looks quite a bit better than your 584. Of course both share the issue of the somewhat dubious calibration (slip of paper/sticker).

Offline Muxr

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Re: Are cheap AD584 units worth it?
« Reply #69 on: June 19, 2017, 04:42:39 pm »
Thanks for posting those measurements! At least your 588 sample looks quite a bit better than your 584. Of course both share the issue of the somewhat dubious calibration (slip of paper/sticker).
No problem. I think you're right. For cross checking handheld DMMs I think it's fine, but I would take the "calibration slip" with a grain of salt. I don't have enough confidence in my lab to determine how much they are off by yet, but even just the 24 hour and TempCo drifts don't seem suitable for anything that has above 5 1/2 digits worth of resolution.
 

Offline mokeman3

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Re: Are cheap AD584 units worth it?
« Reply #70 on: June 20, 2017, 12:38:07 am »
Which leads back to a comment I made earlier: Who here would be willing to spot-check some of these KKmoon devices with an in-call 5-1/2+ digit meter and supply a new slip of paper ?

That's something that I would be willing to compensate someone for.

 

Offline Muxr

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Re: Are cheap AD584 units worth it?
« Reply #71 on: June 20, 2017, 03:26:51 am »
Which leads back to a comment I made earlier: Who here would be willing to spot-check some of these KKmoon devices with an in-call 5-1/2+ digit meter and supply a new slip of paper ?

That's something that I would be willing to compensate someone for.
None of my instruments are recently calibrated (Keithley 2015, Fluke 8045A and 8046A as well as my HP 3458A). However I am getting a new 0.003% reference from Doug (VoltageStandard) this week so I can do a reading of your KKmoon reference once I check my calibration.

It's not ideal but If no one answers your call with an in cal instrument PM me and I can help you out (you don't need to pay me, just pay for shipping).
 

Offline bitseeker

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Re: Are cheap AD584 units worth it?
« Reply #72 on: June 20, 2017, 03:38:47 am »
Well I started reading the cal club thread with the Traveling Reference Concept, and didn't get all the way thru it, but I've sorta lost sight of the goal of it.

Probably better to discuss in the cal club thread, but in short, the current goals include (1) verifying that the roving standard is able to make the loop successfully and in good condition, (2) enabling members at each stop to do the measurements they want and provide some interesting info to the thread, (3) providing opportunities to learn enough to establish goals and improvements (hardware, software, process, etc.) for the next round, and (4) having fun.
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Offline Bud

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Re: Are cheap AD584 units worth it?
« Reply #73 on: June 20, 2017, 05:18:40 am »
There is also this AD588 board.. http://www.ebay.com/itm/111840217453?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

It appears to have better tempco than the best AD584 reference I have.

Lets see....

AD588BQ:
Digikey - $49 Qty 100
Mouser - $47 Qty 100

Completed board eBay from China - $14 Qty 1

Yah... instills trust...Not.
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Offline BU508A

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Re: Are cheap AD584 units worth it?
« Reply #74 on: June 20, 2017, 07:21:15 am »
I've bought one of these (50 pcs of AD587LN) to play around with them:

http://www.ebay.de/itm/162254805543

It claims "SOCKET PULLS", but even in the ebay pictures you can see solder on the pins,
same on mine I've  received. I'll put some photos here this evening.

I'll also try to assemble a 10V reference in the Joe-Geller style (have the same parts as on his reference circuit)
but I have my doubts, that I'm able to achieve the specs of his reference.

Edit: Pictures added

« Last Edit: June 22, 2017, 09:59:54 pm by BU508A »
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Offline Muxr

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Re: Are cheap AD584 units worth it?
« Reply #75 on: June 20, 2017, 12:00:13 pm »
There is also this AD588 board.. http://www.ebay.com/itm/111840217453?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

It appears to have better tempco than the best AD584 reference I have.

Lets see....

AD588BQ:
Digikey - $49 Qty 100
Mouser - $47 Qty 100

Completed board eBay from China - $14 Qty 1

Yah... instills trust...Not.
Same goes for the AD584 based references on eBay. We know they are all salvaged.
 

Offline Bud

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Re: Are cheap AD584 units worth it?
« Reply #76 on: June 20, 2017, 01:30:23 pm »
Ok, but then we can't assume these tests characterise the manufacturer part, these tests only characterise a particular salvaged part, who knows how much abuse it handled, if it was a production reject, a test part, or still can be a fake.
Facebook-free life and Rigol-free shack.
 

Offline alm

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Re: Are cheap AD584 units worth it?
« Reply #77 on: June 20, 2017, 01:42:08 pm »
Agreed. The AD584 units had a fair amount of variation in the amount of noise, and something like that could easily be the case for the AD588 boards. But the only way to tell is to gather data from a large number of units bought over a time span of at least a couple of months.

Of course depending on how they were treated, they might just be well aged references ;).

Offline Muxr

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Re: Are cheap AD584 units worth it?
« Reply #78 on: June 20, 2017, 02:18:03 pm »
Ok, but then we can't assume these tests characterise the manufacturer part, these tests only characterise a particular salvaged part, who knows how much abuse it handled, if it was a production reject, a test part, or still can be a fake.
There is no free lunch. As you put it the brand new part alone costs way more (in both cases AD584 brand new off mouser is $60 just for the part as well). So there is definitely a catch to these ~$15 references from China.

I have 3 ebay AD584 references and one AD588BQ one. And so far AD588BQ sample I have is an improvement over all the AD584's I've tested (at least as far as tempco and noise is concerned (except for occasional popcorn noise), haven't had it long enough to establish long term drift).

But everything you said stands. It's just my samples, the parts are of questionable sources. I am just sharing my data. Your mileage may vary.
 

Offline Marco

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Re: Are cheap AD584 units worth it?
« Reply #79 on: June 20, 2017, 03:10:14 pm »
The only thing is, it requires both a +17V and a -17V rail.

With 16V rated capacitors :)
 

Offline Muxr

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Re: Are cheap AD584 units worth it?
« Reply #80 on: June 20, 2017, 03:34:07 pm »
The only thing is, it requires both a +17V and a -17V rail.

With 16V rated capacitors :)
oops, that's actually my bad. I was thinking of my own prototype reference, the one from China does have 16V rated caps but it requires +15V/-15V.
 

Online Gyro

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Re: Are cheap AD584 units worth it?
« Reply #81 on: June 20, 2017, 03:50:45 pm »
Ok, but then we can't assume these tests characterise the manufacturer part, these tests only characterise a particular salvaged part, who knows how much abuse it handled, if it was a production reject, a test part, or still can be a fake.
There is no free lunch. As you put it the brand new part alone costs way more (in both cases AD584 brand new off mouser is $60 just for the part as well). So there is definitely a catch to these ~$15 references from China.

Ouch! That makes me feel a bit guilty about the tube of 6 unused AD588BQs I scored on ebay a couple of years back for £9.50 including postage. It was genuine UK seller who clears out old production line stores. I think we were both rather surprised when no one else bid! There is still the odd legitimate bargain out there if you keep your eyes open. You guys in the US seem to have it easier in that respect.
« Last Edit: June 20, 2017, 04:10:46 pm by Gyro »
Best Regards, Chris
 

Offline Marco

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Re: Are cheap AD584 units worth it?
« Reply #82 on: June 20, 2017, 05:25:55 pm »
oops, that's actually my bad. I was thinking of my own prototype reference, the one from China does have 16V rated caps but it requires +15V/-15V.

But one of the set of caps is in front of the linear regulators, with room for the drop out you'll exceed the 16V.
 

Offline Muxr

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Re: Are cheap AD584 units worth it?
« Reply #83 on: June 20, 2017, 05:56:28 pm »
oops, that's actually my bad. I was thinking of my own prototype reference, the one from China does have 16V rated caps but it requires +15V/-15V.

But one of the set of caps is in front of the linear regulators, with room for the drop out you'll exceed the 16V.
The datasheet for the AD588 says it can operate with rails down to +/-12V.



Table 3 even references a test with 10.8V +/- rails.

With +15 and -15 supply rails I measured 12.95V (so the drop out is 2V) on the lower rail (at the chip) so it's fine, however it is pretty dumb that they used 16V rated caps pre regulation  |O

edit: I should also add. The caps are after the rectifier and the rectifier has about 0.7V drop as well. So you could technically supply 16V-16.7V +/- rails to the board without operating beyond the cap spec.
« Last Edit: June 20, 2017, 06:08:39 pm by Muxr »
 

Offline jordanp123

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Re: Are cheap AD584 units worth it?
« Reply #84 on: July 09, 2017, 12:07:32 am »
For anyone who has one of these units how have these "Recycled" units been holding up?
 

Offline leonerdTopic starter

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Re: Are cheap AD584 units worth it?
« Reply #85 on: September 26, 2017, 11:12:30 am »
For anyone who has one of these units how have these "Recycled" units been holding up?

I'm just about to get mine re-measured by a cal lab, so I'll let you know when I get a result.

I just hope they don't laugh too much at the look of the quality of the thing. In actuality it isn't too bad inside, it just looks cheap.
 

Offline CJay

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Re: Are cheap AD584 units worth it?
« Reply #86 on: September 26, 2017, 11:29:29 am »
Ouch! That makes me feel a bit guilty about the tube of 6 unused AD588BQs I scored on ebay a couple of years back for £9.50 including postage. It was genuine UK seller who clears out old production line stores. I think we were both rather surprised when no one else bid! There is still the odd legitimate bargain out there if you keep your eyes open. You guys in the US seem to have it easier in that respect.

I'm assuming you have plans for those chips and couldn't be persuaded to part with one?
 

Offline innkeeper

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Re: Are cheap AD584 units worth it?
« Reply #87 on: September 26, 2017, 11:09:41 pm »
I'd love to do some casual comparisons with other references with my kkmoon.
not sure id shell out the bucks to have a cal lab check it., but be nice to cross reference to see how close they are.
i hit ham fests in the northeast USA a lot if anyone else hits them.
Hobbyist and a retired engineer and possibly a test equipment addict, though, searching for the equipment to test for that.
 

Offline BU508A

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Re: Are cheap AD584 units worth it?
« Reply #88 on: September 27, 2017, 05:14:29 am »
Ouch! That makes me feel a bit guilty about the tube of 6 unused AD588BQs I scored on ebay a couple of years back for £9.50 including postage.

I bought yesterday a tube of 14 AD588BD for around U$ 63,- including shipping, taxes, customs etc. Date code is 9239.
http://www.ebay.com/itm/142510140268

Edit: URL changed from .de to .com
« Last Edit: September 27, 2017, 12:37:28 pm by BU508A »
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Online Gyro

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Re: Are cheap AD584 units worth it?
« Reply #89 on: September 27, 2017, 10:48:59 am »
Ouch! That makes me feel a bit guilty about the tube of 6 unused AD588BQs I scored on ebay a couple of years back for £9.50 including postage. It was genuine UK seller who clears out old production line stores. I think we were both rather surprised when no one else bid! There is still the odd legitimate bargain out there if you keep your eyes open. You guys in the US seem to have it easier in that respect.

I'm assuming you have plans for those chips and couldn't be persuaded to part with one?

Yes, mostly allocated (my son wants a couple) but I can probably spare one. PM me your address and I'll stick one in the post.  ;)

Damn, BU508A scored better spec ones!


P.S. If anyone is looking, there appear to be some AD588BQ spec parts available from Germany at what looks like a good price. No idea about the provenance but possibly less likely re-marks from China?  http://www.ebay.co.uk/itm/AD588BQ-Very-High-Precisons-Reference-Voltage-IC-TK-1-5ppm-C-/182764566859?epid=1269035643&hash=item2a8d9df94b:g:Dy8AAOSwi8VZUkGL
« Last Edit: September 27, 2017, 11:21:47 am by Gyro »
Best Regards, Chris
 

Offline BU508A

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Re: Are cheap AD584 units worth it?
« Reply #90 on: September 27, 2017, 12:39:55 pm »
Damn, BU508A scored better spec ones!

Aha? I thought, the BD and the BQ have the same specifications? I did not spot any difference between them in the datasheet.
My impression was, the BD is older than the BQ (probably the BQ is RoHS compliant or something)
What spec's are you referring to? *scratching head*
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Online Gyro

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Re: Are cheap AD584 units worth it?
« Reply #91 on: September 27, 2017, 01:15:44 pm »
Ah no, the ones I bought were JQs. Yours BDs (BQs same) are better.... ~1.5ppm vs my ~3ppm.  :)

I probably confused you with that new ebay link that I spotted.

Edit... Oops, No I did put BQ in my original post didn't I. Mine are definitely JQ.  :palm:
« Last Edit: September 27, 2017, 01:18:32 pm by Gyro »
Best Regards, Chris
 

Offline BU508A

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Re: Are cheap AD584 units worth it?
« Reply #92 on: September 27, 2017, 07:52:45 pm »
Edit... Oops, No I did put BQ in my original post didn't I. Mine are definitely JQ.  :palm:

No worries. Cup of tea? Some bisquits?  :)

Cheers,

Andreas
“Chaos is found in greatest abundance wherever order is being sought. It always defeats order, because it is better organized.”            - Terry Pratchett -
 
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Online 2N3055

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Re: Are cheap AD584 units worth it?
« Reply #93 on: September 27, 2017, 10:46:45 pm »
BD version was made in brazed ceramic package (D-16) (with metal lid), whereas BQ is Cerdip (C-16).. Both hermetic.
Specs seem to be the same.   Brazed ceramic package should be a bit more robust to pin force.. In practice I don't think it matters..
 
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Online Gyro

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Re: Are cheap AD584 units worth it?
« Reply #94 on: September 28, 2017, 09:20:00 am »
Let me try and get my suffixes right today!  :D

I think the BD version was last included in the AD588 Rev A spec. It seems to have gone in Rev B anyway.

I've attached a copy for reference, just in case...
Best Regards, Chris
 
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Offline tszaboo

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Re: Are cheap AD584 units worth it?
« Reply #95 on: September 28, 2017, 10:36:57 am »
Careful with these old AD datasheets. They used accelerated aging to determine the long therm drift, and Linear technology actually debunked the values in them. After this some drift values were changed some two magnitudes (!!!).
 

Online Gyro

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Re: Are cheap AD584 units worth it?
« Reply #96 on: September 28, 2017, 11:05:31 am »
Hard to be able to draw comparisons. Both the Rev A and the latest Rev M datasheets show long term drift as 15ppm/khr @25'C. That implies that either:

A. AD are still using the accelerated method
or
B.  The old accelerated aging method actually correlates with long term aging
or
C. The recent dies have much lower drift than the older ones.

That's got me curious.  :-\

« Last Edit: September 28, 2017, 11:21:35 am by Gyro »
Best Regards, Chris
 

Online 2N3055

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Re: Are cheap AD584 units worth it?
« Reply #97 on: September 28, 2017, 11:31:45 am »
From what I can see on AD588BQ, after initial 10-15ppm drift in first 500-600 hours, now it is very low, below what I can measure  with what I have...

Long term drift for first 1000 hours will be dominated by what it will drift in first 100-200 hours.. Curve is exponential.  If manufacturer would just plug in references for 50 hours before shipping, they could specify much smaller long term drift..

But long term drift will easily be swamped with temp hysteresis effect it you use it trough wide temp range.
AD588BQ that I have seems to be extremely good in that regard as far I can tell.
 

Offline tszaboo

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Re: Are cheap AD584 units worth it?
« Reply #98 on: September 28, 2017, 02:39:29 pm »
Well, if you want to look into it, check out ADR290 datasheet revision A and the current one. And Linear technology DN229.  It should tell a story. I find it amusing TBH. Now AD buying Linear, who will point out these?

15 ppm without maximum value for a hermetic package... sounds about right.
 

Online Gyro

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Re: Are cheap AD584 units worth it?
« Reply #99 on: September 28, 2017, 04:24:55 pm »
Oh yes, I knew about the LT debunking of the AD XFET references.  I guess in the future AD will be responsible for keeping themselves honest!  ;D

I suspect that with a hermetic package buried Zener it doesn't really matter how you age them (within sensible limits), they will always tend to have good long term drift. It may be that AD always did decent sample drift evaluation on these parts, just skimped on the mushrooming number of cheap plastic packaged non-zener types.
Best Regards, Chris
 

Offline dorkshoei

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Re: Are cheap AD584 units worth it?
« Reply #100 on: December 26, 2020, 11:49:07 pm »
So here are my measurements, however not as official as guy48065 has done with one hour warmin etc. just power up two Keithley 2000 not calibrated for at least 8 years but that's all I have here  :)
The K-unit figures are pretty spot on, the L-unit figures are fiction.

I'm seeing a few units advertised with an ad584-m.   Does anyone know about this variant?

"Built-in AD584-M, highest accuracy and stability."

https://www.ebay.com/itm/KKMOON-Accuracy-Voltage-Reference-Module-4-Channel-2-5V-7-5V-5V-10-Hot-Q3D9-/254629183828?_trksid=p2349624.m46890.l49292

« Last Edit: December 26, 2020, 11:54:39 pm by dorkshoei »
 

Offline magic

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Re: Are cheap AD584 units worth it?
« Reply #101 on: December 27, 2020, 01:22:00 pm »
Rev. A datasheet lists -55-125°C temperature grades as S and T, with specs similar to J and K, respectively.

M grade is probably fake. The photographs you linked show the K grade, by the way.
 

Offline jharris1993

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Re: Are cheap AD584 units worth it?
« Reply #102 on: May 24, 2024, 01:09:41 pm »
Quote
NOISE FILTERING
The bandwidth of the output amplifier in the AD584 can be
reduced to filter output noise. A capacitor ranging between 0.01 µF
and 0.1 µF connected between the CAP and VBG terminals further
reduces the wideband and feedthrough noise in the output of
the AD584, as shown in Figure 9 and Figure 10. However, this
tends to increase the turn-on settling time of the device; therefore,
allow for ample warm-up time.

This is the relevant section of the Analog Devices datasheet.
 


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