NI LabVIEW TDMS File Formatting Volume

Updated Apr 12, 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.