How to Achieve Interval Timing on a PXIe-408X DMM

Issue Details

I have a PXIe-408X series DMM and want to use Interval sampling as the sample trigger source. When I try to run my code with the trigger source set to Interval it gives me an error. How do I fix this?

Solution

The PXIe-408X series of NI DMMs are not capable of using interval timing as the trigger source. The closest way to implement interval timing for the 408X modules are as follows:

1. Set the Sample Trigger input on the niDMM Configure Multi Point.vi to Immediate.
2. Add a property node before the niDMM Configure Multi Point.vi to set the Settle Time equal to Sample Interval time that you would use for interval timing.

Your code would look similar to this:
Since interval timing is not an option for the PXIe-408X series of DMM's, adjusting the settling time right before measurements will give a very close alternative. In interval timing, the interval wait time occurs after each measurement cycle. The settling time is a part of the measurement time that occurs rights before the measurement is taken, so it does not affect the aperture time, nor does it affect when you send a trigger. The main difference between interval time and settling time would be the first measure, meaning the first measure would happen a little later using settling time than it would for interval time. This is countered by setting the trigger source to Immediate, adding the Settle Time property node and set it equal to the Sample Interval. 

Changing the settling time will not be the exact same as interval timing, but it is very close.

Additional Information

Additional detailed information on how the PXIe-408X modules of DMM's work can be found in the LabVIEW Help documentation for NI Digital Multimeters. You can find this documentation in LabVIEW by clicking on Help in the toolbar, selecting NI Digital Multimeters Help... and selecting your device under Devices.