Can I Save Measurements to TDMS Files With Different Frequency?

Updated May 2, 2018

Reported In

Software

  • LabVIEW

Driver

  • NI-DAQmx

Other

TDMS

Issue Details

I am acquiring two different signals - Voltage and Temperature with my DAQ device. The measurements have the same sampling rate. However, I don't want to save all the samples from temperature measurement and prefer to have 1 per 500 samples instead. Is it possible to write do TDMS file with different frequency?

Solution

One of the solution for saving data with different rating is shown in teh snippet below:


You can simply eliminate data you don't need to save by calculating average of multiple samples, and save the result only. This helps with managing the memory on the disk. 
The advantage of calculating average instead of saving one in 500 samples is that we don't receive unexpected peak in our measurement file.

Additional Information

There is no need to save all the temperature data to a file, as the changes of it are rather slow. However, the good practice is no to save 1 sample out of 500, but calculate the average and save it instead. 
This can prevent us from receiving big amplitude in between two saved temperature measurements. 

Related Links

The NI TDMS File Format
Read Double data from a device and write these data to TDMS file at two different rates
DAQmx Configure Logging

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