What is a TDMS file?
TDMS (Technical Data Management Streaming) is a binary file format defined by NI. Data is organized in three levels — file, group and channel — and each level can carry properties such as names, units and sampling intervals.
A .tdms_index file sometimes appears next to the .tdms file. It is an index that speeds up reading; the data itself is in the .tdms file.
Ways to open TDMS files
| Method | What it is | Keep in mind |
|---|---|---|
| NI DIAdem | NI's measurement data analysis software, built around TDMS | Commercial software that requires installation |
| TDM Excel Add-In | An Excel add-in distributed by NI that loads TDMS files into Excel | Windows only and requires installation; the worksheet limit of 1,048,576 rows still applies |
| Python (npTDMS) | An open-source library for reading TDMS | Requires a Python environment and code |
| LOGADEC | Time-series viewing and analysis software with no installation | TDMS files saved in the DAQmx raw data format are not supported |
Opening a TDMS file in LOGADEC
- Start it from Try it in your browser, or download the free version and open the extracted HTML file in Google Chrome or Microsoft Edge.
- Click CSV/Excel and choose the .tdms file.
- Each numeric channel appears as a column named "group/channel". The first row holds the channel names and the second the units.
- If there is a time channel (such as Time), it becomes the X axis. Otherwise X is built from the waveform interval stored in the file (wf_increment). If the waveform start time (wf_start_time) is present, it is kept as the start date and time of the data.
- Select the channels you want, click [Import], then click [Select all] in the [Series] tab.
See "Excel and TDMS files" in Loading Data in the user manual for details.
Features often used with TDMS data
- Frequency analysis: FFT, STFT and wavelets for vibration and noise components (Frequency Analysis).
- Filters: low-pass, high-pass, band-pass, notch and more, per series, without changing the source data.
- Anomaly detection: outliers, change points, frequency anomalies and correlation breaks (Time-Domain Analysis).
- Export to CSV: [Export data] writes the loaded TDMS data to CSV, TSV or Excel — handy for converting TDMS to CSV.
- Batch import: [Folder] imports all TDMS files in a folder at once.