I have not been completely volt-nut lazy over the past few months but doing a bit of an experiment - mainly to help me understand voltage references - in both long term drift , temperature and construction of Voltage references. The basis has been TiNs Kx board - again thanks Ilya for sharing your efforts. The reference that TiN evaluated is No 2.
I have 11 voltage references , 10 of which have been powered on continuously since the experiment started in August 2017 (UPS). All Kx have a 2 stage linear regulation power supply, 1st to 18V then to 15V.
Each reference is slightly different - by accident initially - but then expanded. Below is a table of their differences
Ref No LTZ Version Kx Board version OpAmp Resistor type Temp Resistor
1 A early 2057 Vishay z202s 12k
2 A early 2057 Pettis 12k
3 A early modified 2057 Pettis 12k
4 A later 2057 120 Vish, TE-UPW 13.3K
5 C later 1006 TE-UPW 13.3k
6 C later 1006 TE-UPW 13.3k
7 A later 1006 TE-UPW 13.3k
8 A later 1006 120Vish, TE-UPW 13.3k Vish S102
9 A later 1006 Pettis120, TE-UPW 13.3
3458 A 3458s LTZ reference board
Fluke 731b
The boxing/insulation of 4 to 9 are identical.
The set up for each measurement has been similar, 3458 ( a very old one) on for 12 hrs before, room temp >17 for 4 hrs before, heaters/lights off during measurement, DC ACAL, NPLC 100, the same low EMF (Pomona) cables used. Cables left connected for 5 mins before reading taken - draft cover on.
I was a little surprised with the longer term stability of the measurements, I thought I would see more drift, I suppose I am trying to measure "one ruler with 9 very similar rulers" - I can't get around that short of a JJA ! My findings seem to support the comments of some of the more experienced of you do seem to get some "golden" LTZ - some seem to be doing better.
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The graphs below are
1 Orange line; the references change in ppm compared to its average
2 Blue line; the room temperature change in degrees C compared to its average.
The experiment continues.
regards Rob
Edit ; You can see the set up in the photo in Reply 250 above, the Refs 4-9 are on the RHS, Ref 1, 3 and 3458 are inside the Black Box, Ref 2 is outside.