[volt-nuts] Keithley 2002 Q

Frank Stellmach frank.stellmach at freenet.de
Fri Oct 7 00:09:47 UTC 2011

@ mitch:

The 3458A also has the OCOMP feature in the OHM modus (automatic 
substraction of thermal voltages).

Disadvantage is the temperature sensitive, unstable OHM reference, and 
the high timely drift.

A well ventilated cellar improves thingshat a lot .. I managed to reach 
there sub ppm OHM transfer stability (~ 0.2 ppm during 1h), although 
this is not specified at all.

The 1nV resolution is superior on the 2002; the 3458A delivers 10nV only 
via Display (perhaps more and stable resolution via GPIB; I didn't yet 
understand completely the comparison document from Yongbin Leng).

I encountered big programming trouble on the ancient Kethley 195A and 
199A DMMs, should be gone on the 2002, but never saw that on any HP 
boxes. Latter ones firmwares are more stable than anything else to my 

The biggest advantage of the 3458A is the artifact calibration (complete 
AUTOCAL) with only two different sources.

Didn't check, if the Keithley also got this feature, as a better 
differential linearity than 0.2ppm should be required, like in the 
3458A. Frequent AUTOCALl helps to mitigate thermal instabilities, apart 
from its OHM cal drift.


More information about the volt-nuts mailing list