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Synchronized Time Reference

Posted: October 16th, 2018, 12:54 pm
by Matthew V
I am performing an experiment where two currents are measured over time using Keithley Model 6514 electrometers. I don’t necessarily need to measure both currents at the precisely the same time; however, I do need the timestamp associated with each measurement to be in reference to the same time. I am operating at 6 PLC for this experiment, and I am using LabVIEW. Are there any software or hardware solutions? Thanks.

Re: Synchronized Time Reference

Posted: December 4th, 2018, 5:13 pm
by Andrea C
Are you triggering N measurements on each unit? Or doing a software loop and one reading per iteration?

If triggering, it would be advised to put a trigger link cable between the two units and adjust the trigger of N readings so that one meter outputs a "measure now" signal and the other one waits for this.

Re: Synchronized Time Reference

Posted: January 30th, 2019, 5:05 pm
by Matthew V
Thanks for the reply. I was on time crunch and needed to get something working fast.

I ended up using the trigger link on both instrument with a trigger signal generated by a waveform generator. Both electrometers store measurements into the buffer along with a timestamp. Sometimes the clock on one electrometer runs slightly faster than the other. However, I generate my own time stamp based on the period of the waveform generator and ignore the timestamp given by the electrometers. Both electrometers are maintained in the trigger layer with no trigger delay in order to minimize the time between the trigger signal and measurement. I also added two additional instruments that are trigger using the same signal. I didn't use a software loop because the measurement would be too slow with 4 instruments trying to communicate with LabVIEW and I would have less control over the sampling period. Everything has been working great.