Period Measurement | LabJack

Period Measurement

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shahn's picture
Period Measurement


I am measuring the period between two rising edges on FIO4 at 1MHz. The input to FIO4 is a from a magnetic encoder with open-collector output. The period measurement returns a relatively stable value that changes as expected however on occasion I receive a period measurement from the LJ that is considerably different than expected. Has anyone seen this behavior before?

Thanks in advance.

LabJack Support
labjack support's picture
Sorry for the late response.

Sorry for the late response. We just realized now that our response didn't make it to the forum properly as we did have an answer to this a couple days after your post.

Given that your signal is a fairly high speed signal you are probably starting to experience some signal noise in your measurement.  We aren't aware of any firmware issues that would cause this issue.  You will probably need to programmatically handle the noisy measurements. LabJack devices have input protection circuitry designed to make the device more robust than interfacing directly with a microcontroller and this extra circuitry combined with any other external wiring is likely the cause of your measurement imperfections.

It looks like you are using a U3(-LV/HV?). What firmware version do you have on it?