Author Topic: Lowest drift, lowest noise voltage reference (ADR1000AHZ)  (Read 67760 times)

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Online Andreas

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Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #275 on: April 30, 2022, 09:12:22 pm »
Hello,

Update on ageing drift on my ADR#01 + ADR#02 after 40 days (~1 kHr) after adjustments.
ADR#01 first firing was in September last year. Mostly all measurements where done at ~50 deg C.
ADR#02 has ~2kHrs of burn in beginning end of November before final adjustments.

Now I am doing weekly measurements relative to my most stable LTZ#4 reference.
#1 drifted ~1.8 ppm/kHr since adjustments
#2 drifted ~1.2 ppm/kHr since burn in + adjustments.
my newest LTZ#9 (non-A) running since 10/2019 is given for comparison

So #2 seems to have a slight advantage in stabilisation. (but this are only 2 different samples so no significant statistics).
But when I compare that with my AD587 references the ageing drift of the ADR is still too high.

https://www.eevblog.com/forum/metrology/ad587lw-10v-precision-travel-standard/msg4147111/#msg4147111

with best regards

Andreas

 
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Online Andreas

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Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #276 on: May 17, 2022, 08:28:29 pm »
Hello,

update on burn in of ADR1000A#03 now at 2000 hrs (sqrt(2 kHrs))

Cycling is unchanged 110-130 deg C

After trendline changed to -15.5 ppm/sqrt(khr) from 500-1000 hrs (in blue)
the ageing reverted back to the initial ageing rate of -38 ppm/sqrt(kHr) from 1000-2000 hrs.

I will now check wether noise has changed (after downcycling to 50 deg C average).

with best regards

Andreas
 
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Offline branadic

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Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #277 on: May 22, 2022, 07:44:03 am »
I've passed the 7000 h mark, so here's an update. I've rearranged the setup a while ago, removed one of the 2182A and added 34420A instead. The remaining 2182A still monitors the difference between F7000-1 and F7000-2 (green curve), while the 34420A now monitors the difference between ADR1000 and F7000-1 (red curve) and ADR1000 and F70002 (black curve). The magenta curve is the calculated and thus expected difference between ADR1000 and F7000-2. Black (measured data) and magenta (calculated data) curves do match quite well.
While the first plot is a measurement with R6581D monitoring the ADR1000 directly, in the second plot (second measurement each day) the R6581D measures the F7000T (averaged output of the 2x F7000). In plot 2 you can see me messing with the setup at ~2200 h leading to a small jump downwards, that recovers at ~2850 h when I added the 34420A to the setup.
Measurement ongoing.

-branadic-
« Last Edit: May 22, 2022, 08:39:40 am by branadic »
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Online Andreas

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Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #278 on: May 22, 2022, 11:33:02 am »
Hello,

so I still can hope that my ADR1000A will stabilize in some 3-4 kHrs.
At the moment the drift is still  ~1 ppm/month.

with best regards

Andreas
 

Offline sahko123

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Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #279 on: May 25, 2022, 12:11:48 pm »
God I cant wait till I get an ADR1001 put it in a cute little box with a UPS system and seal it away for 50 years
Asking for a friend
 

Online Andreas

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Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #280 on: May 26, 2022, 08:52:53 pm »
Hello,

1/f noise comparison before and after burn on ADR1000#03 in shows no significant change.

on 15.02.2022 the noise was
618 nVpp average with Std dev 62 nV over 19 measurements of 100 sec
and 73 nV RMS average with Std dev 3 nV

today on 26.05.2022 I measured
617 nVpp average with Std dev 77 nV 55 nV over 19 measurements of 100 sec
and 55 nV 77 nV RMS average with Std dev 3 nV

typical noise examples before/after burn in attached.

with best regards

Andreas

edit: corrected interchanged std dev / rms value on 26.05.2022
« Last Edit: May 27, 2022, 05:15:49 am by Andreas »
 
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Offline Kleinstein

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Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #281 on: May 26, 2022, 09:24:59 pm »
The noise curves do look a little different. The RMS noise of 73 and 55 nV is also aready a bit different.
Somewhat looks like the more higher frequency noise could have gone down, maybe the longer lived states causing popcorn like noise got more stable (longer lifetime). If data are available it may be worth looking at the FFT / noise spectrum.
 

Online Andreas

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Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #282 on: May 27, 2022, 05:26:38 am »
The noise curves do look a little different. The RMS noise of 73 and 55 nV is also aready a bit different.

Sorry copy and paste error (RMS noise + std dev interchanged).
Corrected the values above.

In both measurement series I find some "popcorn events (jumps)" of up to 0.3 uV.
So I would not interpret from a single picture (picked to meet about the average peak/peak noise) out of a series too much.

with best regards

Andreas
 
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Online Andreas

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Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #283 on: May 28, 2022, 10:35:16 am »
Hello,

Noise measurements (statistical) can look rather different.
(you have to be at the right place at the right time).

Just some examples: the "best" and the "worst" noise from one and the same measuerment series.
One measurement series before and one after burn in.

The worst case usually also contains one or more edges of some Popcorn events. (which is filtered by the 0.1 Hz high pass filter).
The popcorn events captured here are not necessarily the worst case popcorn events.

With best regards

Andreas


« Last Edit: May 28, 2022, 10:37:30 am by Andreas »
 
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Offline branadic

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Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #284 on: May 28, 2022, 11:01:20 am »
Thanks Andreas, why are you convienced that what you are looking at is popcorn and not some weird emf event nearby? Maybe you can describe your setup a lil bit more detailed and show some pictures?
I guess you have the reference battery powered in a cookie box together with your low noise amplifier, the Picoscope and your convertable disconnected from mains line too? Every potential source of noise/hum is either turned off, banned from your lab or far far away?

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Offline kleiner Rainer

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Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #285 on: May 28, 2022, 11:03:07 am »
I suspect that we have reached levels of sensitivity in our measuring equipment that we have to take events from background radiation and cosmic rays into account. Andreas, do you live in an area with granite rock, think "radon"?

The Wikipedia article about cosmic rays states:
"Cosmic rays have sufficient energy to alter the states of circuit components in electronic integrated circuits, causing transient errors to occur (such as corrupted data in electronic memory devices or incorrect performance of CPUs) often referred to as "soft errors". This has been a problem in electronics at extremely high-altitude, such as in satellites, but with transistors becoming smaller and smaller, this is becoming an increasing concern in ground-level electronics as well.[89] Studies by IBM in the 1990s suggest that computers typically experience about one cosmic-ray-induced error per 256 megabytes of RAM per month.[90] To alleviate this problem, the Intel Corporation has proposed a cosmic ray detector that could be integrated into future high-density microprocessors, allowing the processor to repeat the last command following a cosmic-ray event.[91] ECC memory is used to protect data against data corruption caused by cosmic rays."

If a cosmic ray event can flip a bit in dynamic memory - what could it do to the output signal of a precision reference?

Food for thought.

Greetings,

Rainer

 

Offline Dr. Frank

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Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #286 on: May 28, 2022, 12:03:20 pm »
These spikes extend over longer period of time, instead of a few points only.
Therefore these are highly probable dips coming from the reference, not e.m.f.
2nd argument, other reference does not show such dips. I have observed similar effects on one of my 5 ADR1000 only, scroll upwards, please. These dips did not occur constantly, but there were quiet and noisy phases.
Cosmic rays should not play a role on bipolar, big area semiconductors as such
« Last Edit: May 28, 2022, 12:05:08 pm by Dr. Frank »
 

Offline branadic

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Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #287 on: May 28, 2022, 01:24:59 pm »
Let me remind you of Eric's talk at MM2021 and his explaination of surface charges, so it isn't necessarily popcorn.

Also coupled interference can cause all sort of weird effects. For example I saw weird jumps that appeared to be popcorn noise on my ADR1399. They were invisible to me when I used a 7.5 digit meter because of it's larger noise, but came visible when I switched to an 8.5 digit meter. Both meters where running on the same integration time of 20 s though. It turned out that was some sort of common mode noise from my lab power supply powering the ADR when I switched to my ULNLPS (shielded transformer + LT3045) and these jumps immediately vanished. That effect stressed my head for the last days before I finally found the culprit.

So before drawing any conclusion it's good advice to check that this is not a human induced effect or error, like in 99.9% of the cases. :)

-branadic-
« Last Edit: May 28, 2022, 02:03:53 pm by branadic »
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Online Andreas

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Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #288 on: May 28, 2022, 03:03:07 pm »
Thanks Andreas, why are you convienced that what you are looking at is popcorn and not some weird emf event nearby?

Hello,

of course I am using a metal cookies box connected to the ground of the oscilloscope.
The reference itself and the 1/f amplifier are battery powered.
The scope is powered by a laptop which itself is normally mains powered.
(I have checked that this has only minor effect on the output).

The whole setup is placed in a "quiet" corner of my lab.
Hum is checked by FFT before start of the measurement.
The noise measurements are usually done "over night" where I have less influence from EMI sources.

The question is: how does EMI noise (usually influencing as common mode noise over small parasitic capacitances) look like in comparison to a popcorn noise which is a "rectangular jump in > 1 sec range" (in differential mode) at the output of the 0.1-10 Hz 1/f amplifier.

The simulation shows:
Popcorn noise shows up at each edge as "sawtooth" pulse with a time constant of ~1 sec at the output.

Measurement shows:
EMI-noise (e.g. fluorescent lamp switching) shows up as "short pulse" which is much less in duration in the us or ms range.

and also some weird noise (EMI-pulses from a accidently not disconnected USB-connector) showed up as short pulses with 16 sec regularly time interval.

with best regards

Andreas




 

Online Andreas

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Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #289 on: May 28, 2022, 05:15:09 pm »
For example I saw weird jumps that appeared to be popcorn noise on my ADR1399.

Is there any legend which colour is what?
I see Jumps on the blue line but no real difference between the upper and the lower chart.

with best regards

Andreas
 

Offline branadic

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Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #290 on: May 28, 2022, 06:08:19 pm »
Blue line is the ADR1399 voltage the rest are temperature sensors nearby. The difference is in the scale ;)

-branadic-
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Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #291 on: June 12, 2022, 01:56:25 pm »
Update on ageing drift of my ADR#01 + #02 now ~2 kHrs after adjustment/burn in.

compare also:
https://www.eevblog.com/forum/metrology/lowest-drift-lowest-noise-voltage-reference/msg4189336/#msg4189336

Average drift is now ~1.2 ppm/kHr so -2.4 ppm for the last 2 kHrs.

I have added temperature because my lab temperature is now increasing.
(it is internal temperature of my AD587LW references which are nearby the ADR references so ~2-3 deg C above room temperature).

with best regards

Andreas
 
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Offline branadic

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Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #292 on: July 03, 2022, 08:25:39 am »
I passed 8000 h, hence an update on the diagrams. There is a jump at about 7800 h, which is me pulling my Datron 4000A calibrator from the rack for repair and which the R6581D obviously didn't like  :-DD
From the results measured I was able to create the plots Drift2 and Drift4, which represents what the R6581D would have measured for each reference. Common mode effects on all curves would then represent the LTZ in the R6581D itself, while the rest would belong to the individual reference.

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Online Andreas

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Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #293 on: July 22, 2022, 06:47:24 am »
Hello,

again update on ageing drift of my ADR#01 + #02 now ~3 kHrs after adjustment/burn in.

On day 98 I added a buffer on the 6.6V previously unbuffered output on ADR#01 added some EMI coils + capacitors and put all into a aluminium enclosure. The additional measurement shows that there is no change on output voltage except measurement stray.

The ageing measurements suffer from high lab temperatures of ~30 deg C leading to nearby measured temperatures ~33 deg C of NTC.
So I cannot really tell wether the ageing rate now slows down to ~1ppm/kHr or if it is only due to high lab temperatures.

with best regards

Andreas
 
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Offline branadic

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Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #294 on: August 03, 2022, 08:04:43 pm »
Today, one year ago I've started the measurement of my ADR1000 reference. Here are the results I monitored so far.
New in these series of plots is image Drift3.png, where I've calculated what the R6581 would have measured them, but with the influence of the meter removed (image Drift2.png with common mode effect removed). Note that I've pulled my calibrator from the rack at ~7700h (~4400h in Drift4.png), what influenced the readings of the meter.

Is the reference stable now? Not sure about that, could be that we see this years hot summer as an influence on the ADR, with an overall rise in the lab temperature from 6000h on, while the temperature spikes not being visible. It needs further observation to see how that evolves.

Also interesting to see the difference between both F7000, which is on average 3 µV/year.

-branadic-
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Offline imo

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Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #295 on: August 04, 2022, 07:26:43 am »
..added some EMI coils + capacitors and put all into a aluminium enclosure. The additional measurement shows that there is no change on output voltage except measurement stray..
The most dangerous EMI freq spectra for your measurement is from 50MHz-5GHz today (unless you live close to a powerful long or shortwave transmitter), imho. That filter (on your picture) based on a foil capacitor (good for quite low freq only) and a multi-turn toroid (with rather huge inter-winding capacitance) will work till a couple of MHz effectively.. Better you put 1n-10n ceramics at the binding posts (and at the other side of the choke too) and as the choke a simple 1-3 turn(s) via a small diameter ferrite tube/bead (like the material 52 or 61 for example).
« Last Edit: August 04, 2022, 07:30:53 am by imo »
 

Online Andreas

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Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #296 on: August 04, 2022, 07:21:08 pm »
Hello,

of course you are right in general. Especially with the capacitor value. Best would be a 1 nF feed through capacitor instead of the binding posts.

In my lab WIFI and cell phones are banned.
So most of my EMI are USB cables (@full speed) which are needed to log the voltmeters.

The TN10 ferrites (4A11 material = NiZn) are relative wideband up to some 100 MHz.
https://www.eevblog.com/forum/metrology/emi-measurements-of-a-volt-nut/msg3347342/#msg3347342

with best regards

Andreas

 

Online Andreas

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Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #297 on: September 03, 2022, 05:37:01 pm »
Hello,

again update on ageing drift of my ADR#01 + #02 now ~4 kHrs after adjustment/burn in (up to 2 kHrs).
Setup uses, like before, a ratio measurement against LTZ#4 (my most stable reference) and LTZ#9 as sanity check.

Still having nearly -1ppm/kHr on the zener voltages.

Only the 10V output on ADR#01 seems to slow down.
But I fear that is some humidity influence (seasonal change) of the statistical output divider.

with best regards

Andreas
 
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Offline Dr. Frank

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Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #298 on: September 04, 2022, 10:20:46 am »
Hello,
my ADR1000 #3, currently 6.668563V, is now running for 1 year.
Its oven is set to 51.4°C, and it has got no initial conditioning / heat treatment.

In the diagram, you see its absolute drift, i.e. relative to the median of my group of 8 references.



Over the years, I determined the average drift of this reference group so I'm able to make absolute drift measurements to  < 0.5ppm uncertainty. This is confirmed by the recent 'baseline' measurement of -0.17ppm in June 22, which is derived from the ring comparison organized by branadic, where two members had calibrated uncertainties of < 0.5ppm each, and I, No. 7, was measuring the travelling LM399 right in the middle between both:

https://www.eevblog.com/forum/metrology/eu-calclub/msg4385281/#msg4385281

Therefore, my ADR1000 shows -4ppm/6months when constantly powered between November 2021 and May 2022.
I didn't power it in October 2021, and in June 2022, to check for hysteresis effects.
This turned out to be +2.8ppm in Oct. 21, and up to +2.2ppm in June 22.
On latter tests, I switched it on 12h prior to taking measurements, but in the end did not investigate on how long it takes to reach the previous "warm" value.

I add a comparative drift measurement on two pre-conditioned LTZ1000A, which show -1ppm/6mo. at most, and seem now to stabilize to much smaller drift rates for the last 7 months.



The FLUKE 7000 shows -1.4ppm/year in 2021, which is quite mediocre. So it is used as a stable 10V transfer standard further on, as I changed its output value twice for my experiments on the 752A and 720A dividers.

So my conclusion is, that the ADR1000 at current is not suitable for serving as a volt-nuts reference like the LTZ1000, due to its high annual drift and big hysteresis. A working burn-in procedure would be required. In the datasheet there's a hint that after 3000h @ 75°C the drift will be reduced to 0.5ppm/Yr., but I don't know if anybody has tested this.

Frank
     
« Last Edit: September 04, 2022, 12:30:19 pm by Dr. Frank »
 
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Offline imo

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Re: Lowest drift, lowest noise voltage reference (ADR1000AHZ)
« Reply #299 on: September 04, 2022, 11:43:49 am »
You got the early samples.. Would be better to wait till they fine-tune their production process..  >:D
 


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