Author Topic: AD587LW - 10V precision travel standard  (Read 19299 times)

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Offline Andreas

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Re: AD587LW - 10V precision travel standard
« Reply #100 on: December 13, 2018, 09:02:45 pm »
Another traceable calibration ...

last week I did another calibration on the AD587LW devices
This time against a Fluke 5520A calibrator.

Method: compare Fluke 5520A and AD587LW output voltage (grounds connected)
with a HP34401A as null voltmeter. Average 2 readings with one above and one below zero volts difference on the 34401A.

from calibration protocol Fluke 5520A of 14.05.2018

33V range
displayed: 10000.00  mV
actual:     9999.956 mV  44 uV or 4.4 ppm too low
calculated correction factor: 0.9999956
Uncertainity of 10V calibration according to protocol +/-2.6 ppm (+/-26uV)

We have to use 1 year spec for error propagation:

1 year +/-5 deg C spec Fluke 5520A 12 ppm/reading + 20uV
 10V:   120 uV + 20 uV = 140   uV

uncertainity of AD587LW (10V) calibrations (independant devices -> geometrical added)
 10V: sqrt(sqr(140)+sqr(26))   -> +/-143 uV
(due to the calibration history it should be much less but I have not all protocols)

Unfortunately the AC was off in the lab at that day so the temperature was
at the upper limit of the calibrator specification (28.6 deg C room temperature near calibrator).

AD587LW#2 5520A 28.6 deg C (room) / 30.7 deg C (int)

10000.01  mV -> corrected   9999.966 mV (Fluke) + 0.009 mV (HP)
10000.02  mV -> corrected   9999.976 mV (Fluke) - 0.001 mV (HP)

value 05.12.2018: 9999.975 +/-0.143 mV

so 2 ppm below previous calibration against 3458A and K2002

similarly:

AD587LW#4 5520A 28.6 deg C (room) / 30.1 deg C (int)
10000.01   corrected   9999.966 + 0.005
10000.02   corrected   9999.976 - 0.005

value 05.12.2018: 9999.971 +/-0.143 mV

so 3 ppm below previous calibration against 3458A and K2002

with best regards

Andreas

 
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Offline Andreas

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Re: AD587LW - 10V precision travel standard
« Reply #101 on: April 27, 2019, 07:05:22 pm »
Hello,

I added a 11V TVS diode some weeks ago (see red circle) which has low leakage @10V to protect the output against ESD and (hopefully since I did not actually test it) against a current limited calibrator (if shorted accidently).

As far as I can see the output voltage has not changed by adding the diodes on all 4 samples of AD587LW

For AD587LW#01 + #02 I have now 1 year of ageing data against my LTZ1000s (from which LTZ1000#4 is the most stable).

AD587LW#01 clearly fails my 2 ppm/year target. Its more like 3.5 ppm/year against my LTZ#4.
And ageing also does not look like it will slow down the next time. So I really think that I should do some artificial ageing measures.

The other references are much more stable.
AD587LW#02 is more or less a seasonal change +/- 0.5 ppm against LTZ#4. So within my 2 ppm/year limit.
I guess that this is due to humidity swelling of the EPOXY PCB which influences the AD587LQ reference.
And I think I should exclude LTZ#5 from the averaged diagrams as it spoils the average due to its ageing drift.


with best regards

Andreas
 

Offline imo

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Offline Andreas

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Re: AD587LW - 10V precision travel standard
« Reply #103 on: April 27, 2019, 08:29:06 pm »
Hello,

and the remaining references:

AD587LWB#03: This guy is somewhat suffering from the 2nd order T.C. which could not fully be compensated. So a temperature dependant drift +/- 1ppm over the last months is visible (so within the planned +/-2 ppm for temperature). And it is obvious that it will meet 1 year ageing drift of less than 2 ppm.

AD587LWB#04: It took long time from first measurement until I had calibrated T.C. + full scale on this sample. So only half year data since calibration (day 0).  Ageing drift was -0.5 ppm immediately after calibration.  But since then the device is very stable.

with best regards

Andreas
 

Offline Andreas

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Re: AD587LW - 10V precision travel standard
« Reply #104 on: May 14, 2019, 09:20:26 pm »
Hello,

I made a little instruction leaflet for the AD587LW reference. (see attachment).

with best regards

Andreas
 
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Offline Magnificent Bastard

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Re: AD587LW - 10V precision travel standard
« Reply #105 on: May 16, 2019, 04:37:33 pm »
Sadly, I must report that one of the very best non-ovenized references in the world, the AD587, has transitioned to NRND [Not Recommended for New Designs].  It's now only a matter of time before it goes to EOL [End Of Life].

 :'(
 
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Offline Andreas

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Re: AD587LW - 10V precision travel standard
« Reply #106 on: May 16, 2019, 06:10:08 pm »
Hello,

and the 2nd best one the 5V brother AD586 is now also NRND.
They are crazy.

with best regards

Andreas
 

Offline Macbeth

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Re: AD587LW - 10V precision travel standard
« Reply #107 on: May 16, 2019, 07:51:06 pm »
Since Analog took over Linear and are consolidating, I expect to see the LTZ1000's and LM399's to be killed off in the not to distant future too. Who really needs anything other than a bandgap and then only up to 5V?
 

Offline Magnificent Bastard

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Re: AD587LW - 10V precision travel standard
« Reply #108 on: May 16, 2019, 10:54:49 pm »
Since Analog took over Linear and are consolidating, I expect to see the LTZ1000's and LM399's to be killed off in the not to distant future too. Who really needs anything other than a bandgap and then only up to 5V?

There are an awful lot of LM399's that go into DMMs, so I don't foresee them killing that-- but the LTZ1000 simply does not have enough sales to justify keeping it in the lineup.  If they kill the LTZ1000, that will be a day of mourning for me...  Keysight will have to scramble for a new "super reference" for some of it's high end meters.  There are some manufacturers of voltage references (and other test equipment) that will have to do the same.  This is what happens when the "cake eaters" start making engineering decisions-- disasters ahead!

 :scared:

The AD587 was the last great unheated reference (with low LF noise) that you could buy in a hermetic package.  This decision might cause T.I. to fire up the hermetic packaging line for the REF102-- not as low LF noise as the AD587, but still a good part if you can get it in a hermetic package (that was discontinued long ago).

 :(
 

Offline 3roomlab

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Re: AD587LW - 10V precision travel standard
« Reply #109 on: May 16, 2019, 11:24:36 pm »
I think the next area of exploration is a cooler temperature instead of hotter
in the pickering pdf where they show low temperature drift advantage, there is a plotted point where it is 11k/1k  :-DD
maybe we just need a sweet spot low temperature which forces the drift to stop
maybe a new LTZ with TEC inside instead of heating, it hold the die at maybe -10C. maybe it will never drift or 1ppm per 10 years.

Since Analog took over Linear and are consolidating, I expect to see the LTZ1000's and LM399's to be killed off in the not to distant future too. Who really needs anything other than a bandgap and then only up to 5V?
actually thinking about the history of rivalry, isnt AD the ones dishing out fake stability specifications many years ago?
« Last Edit: May 17, 2019, 12:13:49 am by 3roomlab »
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Offline Andreas

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Re: AD587LW - 10V precision travel standard
« Reply #110 on: May 30, 2019, 09:51:34 pm »
I did it:  I put 2 of the references in the freezer over night 8)  8)

the good news: they survived (packed only into a plastic bag to reduce condensing water) at -19 deg C setpoint temperature.

The other morning the battery indicator blinked: the reference is still running.

The bad news

AD587LW#01 drifted -4.8 ppm
AD587LW#03 drifted -6.2 ppm

against last measurement from sunday. (obviously hysteresis)

so this is a strong indicator that shipping during winter is not the best idea.
And obviously a star pattern is needed to check the reference after each travel.

How long will it need to remove the hysteresis without heating?

with best regards

Andreas




 
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Offline 3roomlab

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Re: AD587LW - 10V precision travel standard
« Reply #111 on: May 30, 2019, 10:43:16 pm »
you going to try 8hr "degauss" ?
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Offline Andreas

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Re: AD587LW - 10V precision travel standard
« Reply #112 on: May 31, 2019, 04:53:38 am »
you going to try 8hr "degauss" ?

Hello,

what do you mean with 8hr degauss?

of course I waited several hours from morning to evening until I measured the voltage output under room temperature conditions.
So I think I will have the offset for several months.

with best regards

Andreas
 

Offline FriedLogic

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Re: AD587LW - 10V precision travel standard
« Reply #113 on: May 31, 2019, 07:15:04 am »
How long will it need to remove the hysteresis without heating?

For a 'winter transfer reference' I'm not sure if you want to remove it.

The question might be more: how do you maintain it?
It's not really the same thing a bench reference that never sees anything but room temperature.

I find that doing a wide range temperature test on a reference which has not had this done on it recently can cause a shift, but subsequent cycles cause much less.

My thinking is that maybe if a reference might get low temperatures, it may be better to always or regularly give it a low temperature. There might be more variation than a reference which never gets wide temperature swings, but it might also get rid of large jumps in the output voltage.

I have plenty 587LQ's to play with, so I can set something up to test how they behave. I'm thinking of doing that with some LM399's too.
 
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Offline 3roomlab

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Re: AD587LW - 10V precision travel standard
« Reply #114 on: May 31, 2019, 02:27:03 pm »


Hello,

what do you mean with 8hr degauss?


Andreas

the hot cold hot cold cycling?
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Online Echo88

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Re: AD587LW - 10V precision travel standard
« Reply #115 on: June 14, 2019, 04:56:22 pm »
Since Analog took over Linear and are consolidating, I expect to see the LTZ1000's and LM399's to be killed off in the not to distant future too. Who really needs anything other than a bandgap and then only up to 5V?

There are an awful lot of LM399's that go into DMMs, so I don't foresee them killing that-- but the LTZ1000 simply does not have enough sales to justify keeping it in the lineup.

Who told you how much they sell and if its profitable to Analog to produce them?
 

Offline Magnificent Bastard

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Re: AD587LW - 10V precision travel standard
« Reply #116 on: June 15, 2019, 03:39:01 pm »
Since Analog took over Linear and are consolidating, I expect to see the LTZ1000's and LM399's to be killed off in the not to distant future too. Who really needs anything other than a bandgap and then only up to 5V?

There are an awful lot of LM399's that go into DMMs, so I don't foresee them killing that-- but the LTZ1000 simply does not have enough sales to justify keeping it in the lineup.

Who told you how much they sell and if its profitable to Analog to produce them?

My Linear Tech (now Analog) Rep.  He didn't exactly come right out and SAY that, but "reading between the lines" of what he DID say is how I arrived at that conclusion.  This was said just before the Analog takeover.  Analog is a vastly different company than it used to be, and is a vastly different company than Linear Tech used to be-- I don't think they would hesitate one second to drop a device from their lineup if it was losing money-- and ESPECIALLY if they had to pump a lot of money into an old fab just to keep it going, so that a few old parts can continue to be produced.  The only thing that is saving us is contractual obligations-- which I am not privy to-- but I know they must exist.  One good place to find out is Keysight-- they would know if there are rumors about these parts going NRND.  Keysight would have to scramble to come up with an alternative to the LTZ1000 and the LM399--- I have something in mind, but to think Keysight would listen to ME is laughable.
 
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Offline Crossphased

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Re: AD587LW - 10V precision travel standard
« Reply #117 on: June 17, 2019, 08:09:26 am »
How do you guys feel about AD588? Looking at specs it has better tempco than AD587, and slightly lower p-p noise. Its also available in Cerdip, although it is more pricey than AD587. Its pin programmable to +10,+5, +-5, -10  so it can potentially fill in for the AD586 or AD587. Anybody have experience with this ref?
 

Offline Andreas

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Re: AD587LW - 10V precision travel standard
« Reply #118 on: June 18, 2019, 06:43:40 pm »
How do you guys feel about AD588? Looking at specs it has better tempco than AD587, and slightly lower p-p noise. Its also available in Cerdip, although it is more pricey than AD587. Its pin programmable to +10,+5, +-5, -10  so it can potentially fill in for the AD586 or AD587. Anybody have experience with this ref?

Hello,

not myself but Lars reported on 25.11.2015 on "volt-nuts" about the AD688:
https://www.mail-archive.com/volt-nuts@febo.com/msg02662.html
Of course it is only a single sample and "popcorn noise" can occur on every reference.
But external temperature compensation seems to be difficult.

But I would only use a AD588/688 if I really need dual reference voltages.
And I would shurely not use the internal OP-Amps (1uV/K) for generating the buffered outputs.

with best regards

Andreas
 

Offline Andreas

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Re: AD587LW - 10V precision travel standard
« Reply #119 on: June 18, 2019, 08:13:34 pm »
Hello,

on our volt nut meeting in Stuttgart I got another 2 traceable calibrations for my best 2 devices AD587LW#02 and AD587LW#04.
One against freshly calibrated 3458A from Branadic. The other as transfer in 10V range of 3458A compared to the Fluke 7000.

Attached you find the diagrams with the measurement uncertainities.
It seems that AD587LW#02 has nearly no ageing drift whereas AD587LW#04 drifted 1 ppm down during calibrations.

with best regards

Andreas

 
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