Why TDMS does not look like an Excel sheet
TDMS is a measurement file format with a hierarchy of Groups and Channels, as well as properties and timing information. An Excel worksheet is a two-dimensional table. Moving data between them usually means choosing which Channel values you want in a table.
Excel can import CSV files, but a native TDMS file is not itself a CSV or an .xlsx workbook. You generally need a TDMS-aware tool, script, or compatible add-in to read the measurement and prepare the values for Excel.
First, find the Channel you actually need
Before converting anything, check the TDMS Groups and Channels, the sample count, and the data type. If a file contains many Channels, importing all of them may make the spreadsheet harder to use rather than more useful.
TdmsSlice can show the Channel structure and metadata. Quick Preview is available for supported data types so you can inspect an overview before picking an export range.
A practical TDMS to CSV to Excel workflow
When your goal is a manageable worksheet, export the required sample range from one TDMS Channel as CSV, then import that CSV into Excel. The important decision is what portion of the measurement the spreadsheet task needs.
- Open the original TDMS file with a TDMS-aware reader such as TdmsSlice.
- Select the Group and Channel required for your analysis.
- Check the sample count and use Quick Preview if supported.
- Choose Start index and Count to define the samples you need.
- Export the selected Channel range to CSV; retain the companion metadata JSON.
- In Excel, use Data > From Text/CSV (or your version's equivalent) and check the imported column types before working with the values.
Check the Index, time, and data types
TdmsSlice's CSV includes an Index column with the original Channel sample index, even when the selected range begins far into the recording. This helps connect spreadsheet rows to the TDMS source.
If usable waveform timing information is present, a derived time column may also be included. A separate Channel named time or Timestamp is not automatically joined to another Channel. String, raw Timestamp, and Complex data can also require different CSV representations.
When importing a CSV, check that Excel has interpreted identifiers, timestamps, decimal values, and other fields as intended. Keep the metadata JSON with the exported CSV so the source context is not lost.
What if the TDMS data is too large for Excel?
Excel worksheets have a limit of 1,048,576 rows. If your CSV has a header row, that header also occupies a worksheet row. A CSV file itself does not inherit this worksheet row limit, so exporting an enormous CSV is not necessarily a solution to the Excel problem.
When only a short time window or event matters, choose that range while the file is still in TDMS, then export the subset. If you genuinely need to process every sample in a very large measurement, a scripting or dedicated analysis workflow may be more appropriate than an ordinary worksheet.
What TdmsSlice does and does not export
TdmsSlice focuses on inspecting TDMS files and exporting a chosen sample range from one Channel to CSV, with a separate metadata JSON. It is not a direct TDMS-to-.xlsx converter, a multi-Channel joiner, or a full spreadsheet or DIAdem replacement.
Quick Preview and CSV availability vary by data type and structure. Evaluation CSV export is limited to 100 samples per export. Check the Download page for current availability and the product documentation for supported behavior.