The TDM data model supports two file formats: TDM and TDMS. These formats differ in how they store metadata, in what functionality they support, and in what operating systems they support.

  • TDM—(Windows only) The TDM file format saves the raw data that the measurement hardware acquires and the metadata in separate files. Metadata can be the name and unit of a measurement channel, the name of the test engineer, and other information. The metadata 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 metadata 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 these formats to store measurement data. The following table helps you decide which file format is more suitable to your application.

    Functionality TDM TDMS Notes
    Cross-Platform Support

    No

    Yes

    		 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

    No

    Yes

    		 Requires DAQmx 9.0 or later.
    DIAdem Support

    Yes

    Yes

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

    Yes

    Yes

    		 Requires LabWindows/CVI 8.1 or later.
    Measurement Studio Support

    No

    Yes

    		 Requires Measurement Studio 8.6 or later.
    LabVIEW Toolkit Support

    Yes

    Yes

    		 The TDM and TDMS file formats work with the DataFinder Connectivity VIs. The TDMS file format also works with the following LabVIEW toolkits and modules:
    • LTE Measurement Suite 1.0 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

    No

    Yes

    		 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

    No

    Yes

    		 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

    No

    Yes

    		 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

    Yes

    Yes

    		 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.