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3458A Measurement sequence, OCOMP and AZERO ON

Question asked by vcshamoen on Nov 27, 2013
Latest reply on Dec 10, 2013 by jdwindrvr
What is the measurement sequence of an OHMF measuring 3458A with OCOMP and AZERO both ON?

I'm measuring a resistor with with an 3458A in OHMF mode and I'm interested in the path the voltage takes during the integration, as this resistor is actually a thermistor, which means the resistance varies strongly during integration. That's why I'm sampling the voltage(sense) of the OHMF-DMM with another 3458A. I'm using both OCOMP and AZERO for better quality resistance measurements. For the sake of synchronization, the second (sampling) DMM is triggered by the aperture waveform of the first, so that the voltage measurements coïncide with the resistance measurement.

I noticed per resistance reading, I get four readings from the sampling DMM (MEM FIFO) which are probably the actual value (used to eventually calculate the resistance), the OCOMP reading and some AZERO's. The problem is, I don't know which is which. The manual contradicts itself saying the OCOMP without source current is done prior to the measurement (page 209), while it says on page 62 that the genuine reading (current on) is done first, and followed by an OCOMP (cuurent off).

My measurement data reveals first two samples with current on, followed by two samples without current. Does anyone know the actual order of the measurement sequence? My best guess so far is the genuine reading first, followed by an AZERO (current on with both), then the OCOMP with yet another AZERO (current off).

Edited by: vcshamoen on Nov 27, 2013 8:58 AM