NI LabVIEW TDMS File Formatting Volume

Updated Oct 25, 2023

Reported In


  • Multifunction I/O Device


  • LabVIEW


  • NI-DAQmx

Operating System

  • Windows

Issue Details

I have multiple NI data acquisition (DAQ) devices.
When I acquire data (DAQmx Read (VI) multiple channels) and then merge them in to one TDMS file by using TDMS Write Function, the resulting file volume is bigger than if acquisition was done by using DAQmx Configure Logging (VI) . Similarly if I already have multiple TDMS files saved with DAQmx Configure Logging (VI) and I merge them into one, resulting file size is greater than the sum of "parent" file volumes.
How can I reduce the file size?


DAQmx Configure Logging (VI) is built for high-speed streaming to disk, therefore it has built in optimization algorithms for data logging. It compress data while forming a file. In conventional TDMS converting VIs, this compression is not performed.
This is why converting in to TDMS and/or merging files into one will have greater volume.
If data volume is critical for your application use DAQmx Configure Logging (VI) to reduce file size.

Additional Information

With NI-DAQmx 9.0 or later, TDMS file writing is now directly integrated into the NI-DAQmx driver for the easiest and fastest way to stream data to disk reaching speeds up to 1.2 GB/s.