Displaying Absolute Time from TDMS Data in Excel

Updated Dec 4, 2019

Reported In

Software

  • DIAdem
  • TDM Excel Add-In

Issue Details

  • Is there a way to configure the Excel TDM Importer to display absolute time for my waveform data?

  • When importing my TDMS file to Excel, relative time is displayed. Can I change this to absolute time?

  • Can I choose to display absolute time instead of relative time in Excel?

Solution

The Excel TDM Importer displays relative time by default. There are no importer configurations to change this.
However, absolute time can be displayed by generating a time channel in DIAdem beforehand or by calculating time in Excel.

Note that this is only suitable for waveform data types. When working with numeric data, no time stamp is associated.
For more information on how to add time stamps to a file, see Include a Time Stamp in a File Using the Write To Measure File VI.


Generate a Time Channel in DIAdem

1. In DIAdem, waveform data is comprised of numeric and time information. The waveform data must be converted to an equivalent time channel and numeric channel.

2. Navigate to the Analysis Tab in DIAdem. From the Toolbar, select Channel Functions >> Numeric Channels <-> Waveform Channels...



 

3. In the pop-up window, choose the waveform channel to convert in the "Channels" section. Ensure that the remaining configurations are set as shown in the below image:

 

4. Once this has been configured, select "OK" in the dialog box. The Data Portal should now display a time channel and an equivalent numeric channel for the waveform data as shown.

5. The TDMS file can now be saved. When opening the edited file with the Excel TDM Importer, an absolute time column is now included.



Calculate Time in Excel

When opening a TDMS file in Excel, the first worksheet contains information about the channel configurations. The measured data is stored in a separate worksheet.

1. Firstly, find the time information within the first worksheet. For this, the "wf_start_time" and "wf_increment" are required. This is usually located further across in the worksheet, as shown below:

2. Copy this information into the worksheet containing the channel data. This will be used as a reference in the time formula.

3. In the channel data worksheet, create an "Absolute Time" column. In the first cell, the following formula can be used:

4. Press Enter, and the first "Absolute Time" cell should contain the waveform start time. Click and drag the cell down to complete the remaining cells in the column. The column should now be populated with the time that the measurement was recorded, as shown:

Additional Information

Waveform data is automatically recorded with respect to time. When viewing the generated TDMS file in DIAdem, no time column is visible in the channel table.

This is because the channel table displays manually configured channels only. An individual time column is only included if a time channel is created separately in DIAdem.