Editing Properties (sampling time) of a TDMS file

[hazlekatie]

Hello,

I am using a WSN 3214 to collect strain data from strain gauges, and then I'm writing the data to a tdms file to analyze it. When I open the tdms file, each channel says the wf_increment is 0.1 (sampling at 10 samples/sec). How can I change this value so I'm sampling at 100 samples/sec (wf_increment = 0.01)?

Thanks!

[xl600]

Wf_increment is written to tdms based on the dt value in the waveform you wired into the tdms write vi.  Changing it in the tdms file is "after the fact" and won't change anything real.  All it would do is change the dt value of the waveform data you read from the tdms file.

I believe you want to alter how you are reading your strain gauges via daqmx.  You will need to alter your task sample rate and read sizes.

[hazlekatie]

Yeah, I can see that changing wf after the fact doesn't help to change the sample time for the next time I run the VI. But since I'm using the WSN 3214, I don't go through daqmx to read the strain values. The node has it's own properties to set the sample rate and waveform, but changing these values doesn't change anything in the tdms file, so I'm unsure of where else I can access that wf_increment, before it gets written. I've attached photos of my VI and the properties for the node for reference.

[Ben]

look closely at the dt of both charts to ensure that both the half and the full are running at the same dt.

Ben

[hazlekatie]

Thanks, Ben - yes both channels (charts) are running at the same dt - 10 samples per second. I want to edit that dt however, so that it runs at 100 samples per second instead, but I cannot find the option to change this value.

[xl600]

I don't know how to use the WSN devices.  A quick search resulted in this link and this link though.  Those appear to be where the default sample rates are configured (Dialog and a configuration VI).  It's not the dt value that you need to change.  The dt value is filled in based on the device setup.