One cold winter day I received a message informing me that a package is underway and I should expect it in no time. Indeed, a guard in blue, red, orange and yellow striped uniform appeared and handed me an urgent package containing a powered ADR1001 reference, built by Imo, a valued member of this community.
Since I had only a few days before he returned to pick up this valuable cargo, I started a quick evaluation of this reference.
1, At first I went for noise measurement. My setup consisted of DUT, connected to LFLNA-80 preamplifier, followed by HP34401A triggered by Rigol DG822 function generator to obtain a 25Hz sample rate.
Three measurements were performed, with various DUTs - a 50R termination resistor (logged as 25SPS_n-50r.csv), then ADR1000 containing ADRMU reference from Marco Reps (logged as 25SPS_adrmu.csv) and finally, reference from Imo (25SPS_im.csv filename).
Python script was used to generate a NSD chart attached below (see 1_NSD_result.png). It is obvious that ADR1001 in this circuit (utilizing its internal scaling resistor and amplifier) does exhibit higher noise than ADR1000 with scaling resistors and an amplifier, especially at lower frequencies.
2, Then I connected the reference to Datron1281 DMM and logged voltage overnight. I measured ADR1000 based reference under similar conditions. Measured values were visualized in a chart, and for both logged charts I added a 20 point long moving average to point out the low frequency noise somehow better, see 2_6h_log.png
This measurement confirmed previous findings - ADR1001 in this circuit seems more temperamental than the ADR1000 reference.
3, Last test I performed was a rough temperature coefficient test. I left the reference enclosure thermally insulated and the loss heat from its PSU did the rest. Over the course of a few hours internal temperature slowly rose by 6 degrees Celsius from healthy 37,5 to over 43 degrees. HP34401 logged the voltage from an LM35 sensor near the ADR1001 IC, built into the reference circuit by Imo. Logging this data and the reference voltage provided me with an indication of the reference temperature coefficient. See the picture 3_tempco.png
The result is relatively noisy and it's difficult to put a good trend line over the data, but it seems like the sensitivity is a bit below 1uV per degree Celsius in this narrow temperature range (though probably wide enough for lab use).
At this point I had to return the reference box to its author. Results of the processed data are below, as well as source data in case anyone wants to play along.