Precise Offset Compensation Ohm Measurements and Validation of DMMs

[quarks]

Unfortunately I totally missed this very interesting information until today.
Great post, many thanks for sharing.

[dr.diesel]

Unfortunately I totally missed this very interesting information until today.

Yeah, I can't keep up anymore either.  Sure wish @mentions worked!   

[dl1640]

Very informative investigations. I set up a 3458A with OCOMP DELAY5 NPLC100 4W to check a 100 ohm class .005 resistor, I'm going to see how good it can get. The resistor is obviously out of spec and I need to use it by this calibrated value.

[Dr. Frank]

Very informative investigations. I set up a 3458A with OCOMP DELAY5 NPLC100 4W to check a 100 ohm class .005 resistor, I'm going to see how good it can get. The resistor is obviously out of spec and I need to use it by this calibrated value.

This delay is necessary only for R >= 10k.
For 100Ohm, you can have a delay of a few ten msec, otherwise you waste time.

Frank

[dl1640]

Thanks Frank,
I will try different delay time.

[Smokey]

I just picked up a Keithley2700 with OCOMP. 
https://download.tek.com/manual/2700-900-01K_Feb_2016.pdf

There is no mention of NPLC related to that OCOMP process.  In fact they only let you select "fast"=0.1NPLC, "Medium"=1NPLC, or "Slow"=5NPLC from the front panel for measurements.  Using GPIB NPLC can be set up to 50, but that's it.

Update:  Just ran a test.  24Ohm resistor, 4W-OCOMP.  Square wave type signal with about +/-18mV.
Slow = 2.1Hz
Medium = 8.6Hz
Fast = 17.7Hz