Scale Values When Using the DAQmx Configure Logging (TDMS) VI in LabVIEW

Updated Jan 9, 2025

Reported In

Software

  • LabVIEW

Driver

  • NI-DAQ™mx

Issue Details

  • When reading the property values of a TDMS file written with the DAQmx Configure Logging (TDMS) VI in LabVIEW, I see some scale lines, I am not using any scale in my tasks. Where do those lines come from?

 

Solution

The scale lines appearing in the TDMS files written with the DAQmx Configure Logging VI in LabVIEW are expected. The function is designed to optimize throughput and file size by logging unscaled binary data to the TDMS file. As a result, it also writes the channel's scaling expression to the TDMS file, so that you can read the data in F64 format with the correct units for the channel's measurement type. For many devices, this scaling expression also includes the device's calibration scaling.

Additional Information

The file size produced with DAQmx Configure Logging is 2x or 4x smaller than the file size produced by logging F64 data, since it contains I32 or I16 data.