TDM versus TDMS

LabVIEW 2018 Help


Edition Date: March 2018
Part Number: 371361R-01
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TDM data model supports the following two file formats:

  • (Windows) TDM—The TDM file format saves the raw data that the measurement hardware acquires and the meta data in separate files. Meta data can be the name and unit of a measurement channel, the name of the test engineer, and other information. The meta data is in the XML format with the .tdm extension. The raw data is in a compact binary format with the .tdx extension.
  • TDM Streaming (TDMS)—The TDMS file format saves both the raw data and the meta data in the binary format in one file with the .tdms extension.
    Note  When creating or opening a .tdms file, LabVIEW might automatically create a .tdms_index file. LabVIEW uses the .tdms_index file to speed up random access to the .tdms file. The .tdms_index file is optional in TDMS applications. If you have disk space limitations, configure the TDMS Open function to stop generating this file.

You can use either of them to store measurement data. The following table helps you decide which file format is more suitable to your application.

TDM TDMS Notes
Cross-Platform Support

The TDM file format supports Windows only. The TDMS file format supports Windows, macOS, Linux, and real-time operating systems such as Phar Lap ETS, VxWorks, and NI Linux Real-Time.
DAQmx Support

Requires DAQmx 9.0 or later.
DIAdem Support

Requires DIAdem 10.0 or later.
LabWindows™/CVI™ Support

Requires LabWindows/CVI 8.1 or later.
Measurement Studio Support

Requires Measurement Studio 8.6 or later.
LabVIEW Toolkit Support

The TDM file format works with the LabVIEW DataFinder Toolkit. The TDMS file format works with the following LabVIEW toolkits and modules:
  • DataFinder Toolkit 1.0 or later
  • LTE Measurement Suite 1.0 or later
  • MathScript RT Module 8.5 or later
  • Simulation Interface Toolkit 4.0 or later
  • Statechart Module 2.0 or later
  • Sound and Vibration Measurement Suite 7.0 or later
Complex Data Support

In addition to supporting all data types that the TDM file format supports, the TDMS file format also supports other data types, such as single-precision and double-precision complex floating-point numbers.
High-Speed Data Streaming Support

LabVIEW includes the TDM Streaming VIs and functions that you can use to stream TDMS data at a high speed. However, LabVIEW does not provide such VIs or functions for the TDM file format.
Advanced File Operations Support

In addition to the standard TDM Streaming VIs and functions, LabVIEW also provides advanced VIs and functions, which enable you to stream TDMS data synchronously or asynchronously. However, LabVIEW does not provide such VIs or functions for the TDM file format.
Data Subset Removal Support

For TDM files, you can use the Delete Data VI in LabVIEW to remove a channel group or channel. For TDMS files, you can use the TDMS Delete Data function in LabVIEW to delete data from a channel or multiple channels in a group.

Related Information

TDM Data Model

Interacting with TDM Files

Interacting with TDMS Files

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