I do have the display off, auto zero off, fixed range and low resolution. I want each meter to trigger at the same time, but they jitter about +/- 100 us from each other.
I’m sorry John. Something is wrong with my test setup. I’m getting very inconsistent results both with two 34401As and with two 34461As. The main thing I’m seeing with the 34401As is that there is a constant offset between the 10 VCM pulses for the two DMMs, but it is different for every test run and is anywhere from a couple of us up to near 100 us. Sometimes it doesn’t respond to the bus trigger at all.
Best regards,
Tom
Tom Conway
Technical Support Engineer Keysight Technologies
Tom_Conway@non.keysight.com<mailto:Tom_Conway@non.keysight.com> 900 South Taft Avenue
970-679-3842 Loveland, Colorado 80537-6378
Hi John,
I discussed this with the 34401A project manager and he told me that this is expected and is the reason the GPIB bus trigger synchronization is not specified. The GET operation is very complex and the old slow processors in this 25 year old DMM just can’t do any better. Multiple unit synchronization with GPIB Bus Trigger (Group Execute Trigger) is not specified for even our newest DMM models. Sorry. External Trigger is, but that is not a software bus trigger.
Best regards,
Tom
Tom Conway
Technical Support Engineer Keysight Technologies
Tom_Conway@non.keysight.com<mailto:Tom_Conway@non.keysight.com> 900 South Taft Avenue
970-679-3842 Loveland, Colorado 80537-6378
Thanks for testing.
I changed my strategy and am triggering using a sync pulse from the signal generator (there's another problem with the 33120A where enabling/disabling sync resets the waveform phase), but I still get ~ 100 us jitter with 34401A's. I tested a 34465A and it's much better -- within us. I didn't get a chance to check with a 34410A yet...
Edit -- I checked with a 34410A -- the delay from trigger to VM complete is constant within about 1 us (the actually delay depends on resolution etc. The display is on, but the internal architecture of the meter is different and the ADC MCU is not kept busy by the display). That's good enough for me (except I don't have two of those).
Thanks for the feedback, John.
Best regards,
Tom
Tom Conway
Technical Support Engineer Keysight Technologies
Tom_Conway@non.keysight.com<mailto:Tom_Conway@non.keysight.com> 900 South Taft Avenue
970-679-3842 Loveland, Colorado 80537-6378
I saw the same thing until I turned the display off. Then it worked as expected and the samples occurred simultaneously.