Electronics > Metrology

Lowest drift, lowest noise voltage reference (ADR1000AHZ)

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imo:

--- Quote from: Andreas on July 22, 2022, 06:47:24 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..

--- End quote ---
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).

Andreas:
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

Andreas:
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

Dr. Frank:
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
     

imo:
You got the early samples.. Would be better to wait till they fine-tune their production process..  >:D

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