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My LB02A vs my new Brymen BM869s vs Keithley 2000 vs HP 34401

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jorgemef:
Hi,

With additional measurements I tracked the noise to something introduced through the LM358.
DAC output seems very litle noise (3-4 uv) and feeds OP07C in+ and LM358 IN+b through 10K resistors.
Adding voltage measured on these opamp for the different voltage settings. Noise pops on the LM358 from time to time and vanishes again after some time.
Well, 300uV of noise even at 1v output is still within tolerance range of 0,025%. :)

Cheers,
Jorge

GnomeZA:

--- Quote from: J-R on November 24, 2022, 10:34:08 am ---Just tested my calibrated HP 34401A (cal data @ 72.8F) and un-calibrated but known good Keithley 2015 THD. Ambient was 63.7F.   All tests run within 10 seconds of a completely cold power-on using a fully settled PDVS2mini:

34401A was 48 counts high at 100mV, 11 counts low at 10V.

2015 THD was 32 counts low at 100mV and 14 counts low at 10V.

I've used both of these quite a bit and just have not found them to require extensive time to settle, unless I'm using every last digit to compare against calibrated references in volt-nut mode.  In that case I also break out the Keithley 2010, get the room to 72F and let everything simmer for half the day...

Anyway, this is just one data point, perhaps others can post their results.

--- End quote ---

My experience mirrors yours.  I have a AD584 that is powered on for a few months now from battery and my K2000 drops about 5 counts from cold to powered on for hours.  Getting this exact same experience now months later.  I've even written down the "cold" and "hot" measurements.

I know this isn't the most extensive test, but it is the best I have to measure drift.

I mention months because what this is in an apartment in the southern hemisphere that has gone from winter to summer and low(er) humidity to high(er) humidity.  So fairly remarkable result as far as the K2000 is concerned really.

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