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Write Metadata to TDMS File

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This example shows how to write file properties, channel group properties, and channel properties to a TDMS file.

For this example, you have measurents of revolution and electrical current of a circular saw in a scenario where it stops on detecting contact with skin. You can write these measurement to a new TDMS file, update the default properties, and add custom properties to the file, channel group, and channels.

Set Up Workspace

Read the data into the workspace and define the TDMS file channel group names.

load("sawstopper.mat")
fileName = "sawstopper.tdms";
channelGroup = "SawData";
channelRev = "Revolutions (1/min)";
channelCurrent = "Current (A)";

Create the TDMS file, and then read and view its data.

tdmswrite(fileName, circular_saw_data, ChannelGroupName=channelGroup, TimeChannel="none");
stackedplot(tdmsread(fileName, TimeStep=milliseconds(0.0028)))

Write File Properties

Observe the default file properties.

tdmsreadprop(fileName)
ans=1×5 table
          name           description          title           author              timestamp          
    _________________    ___________    __________________    ______    _____________________________

    "sawstopper.tdms"        ""         "Saw Stopper Data"      ""      2022-04-26 13:14:31.675516000

Update the title property using tdmswriteprop, and add a new custom timestamp property set with the current datetime.

tdmswriteprop(fileName, "title", "Saw Stopper Data");
tdmswriteprop(fileName, "timestamp", datetime("now"));
tdmsreadprop(fileName)
ans=1×5 table
          name           description          title           author              timestamp          
    _________________    ___________    __________________    ______    _____________________________

    "sawstopper.tdms"        ""         "Saw Stopper Data"      ""      2022-04-26 13:15:23.350898000

Write Channel Group Properties

Observe the default channel group properties.

tdmsreadprop(fileName, ChannelGroupName=channelGroup)
ans=1×3 table
      name               description                          scenario               
    _________    ___________________________    _____________________________________

    "SawData"    "Circular Saw Measurements"    "Stop on detecting contact with skin"

Update the channel group property description. Then add a custom property scenario to the channel group.

tdmswriteprop(fileName, "description", "Circular Saw Measurements", ChannelGroupName=channelGroup);
tdmswriteprop(fileName, "scenario", "Stop on detecting contact with skin",ChannelGroupName=channelGroup);
tdmsreadprop(fileName, ChannelGroupName=channelGroup)
ans=1×3 table
      name               description                          scenario               
    _________    ___________________________    _____________________________________

    "SawData"    "Circular Saw Measurements"    "Stop on detecting contact with skin"

Write Channel Properties

Similarly, you can update the channel properties such unit_string by specifying the channel group name and channel name.

tdmsreadprop(fileName, ChannelGroupName=channelGroup, ChannelName=channelRev)
ans=1×8 table
            name                          description                  unit_string            wf_start_time            wf_start_offset    wf_increment    wf_samples            formula         
    _____________________    ______________________________________    ___________    _____________________________    _______________    ____________    __________    ________________________

    "Revolutions (1/min)"    "Rotational speed of the circular saw"       "rpm"       2022-04-19 14:18:32.304446999           0             2.8e-06         23572       "rpm = frequency(Hz)/60"


tdmswriteprop(fileName, "unit_string", "rpm", ChannelGroupName=channelGroup, ChannelName=channelRev);
tdmswriteprop(fileName, "formula", "rpm = frequency(Hz)/60", ChannelGroupName=channelGroup, ChannelName=channelRev);
tdmswriteprop(fileName, "description", "Rotational speed of the circular saw", ChannelGroupName=channelGroup, ChannelName=channelRev);
tdmsreadprop(fileName, ChannelGroupName=channelGroup, ChannelName=channelRev)
ans=1×8 table
            name                          description                  unit_string            wf_start_time            wf_start_offset    wf_increment    wf_samples            formula         
    _____________________    ______________________________________    ___________    _____________________________    _______________    ____________    __________    ________________________

    "Revolutions (1/min)"    "Rotational speed of the circular saw"       "rpm"       2022-04-19 14:18:32.304446999           0             2.8e-06         23572       "rpm = frequency(Hz)/60"

You can also specify arrays of property names and values. If the property values have different data types, use a cell array.

tdmsreadprop(fileName, ChannelGroupName=channelGroup, ChannelName=channelCurrent)
ans=1×7 table
        name                  description             unit_string            wf_start_time            wf_start_offset    wf_increment    wf_samples
    _____________    _____________________________    ___________    _____________________________    _______________    ____________    __________

    "Current (A)"    "Current in the circular saw"        "A"        2022-04-19 14:18:32.304446999           0             2.8e-06         23572   


tdmswriteprop(fileName, ["description" "unit_string"], ["Current in the circular saw" "A"], ...
    ChannelGroupName=channelGroup, ChannelName=channelCurrent);
tdmsreadprop(fileName, ChannelGroupName=channelGroup, ChannelName=channelCurrent)
ans=1×7 table
        name                  description             unit_string            wf_start_time            wf_start_offset    wf_increment    wf_samples
    _____________    _____________________________    ___________    _____________________________    _______________    ____________    __________

    "Current (A)"    "Current in the circular saw"        "A"        2022-04-19 14:18:32.304446999           0             2.8e-06         23572

Examine the property settings in the ChannelList display.

info = tdmsinfo(fileName);
info.ChannelList
ans=2×8 table
    ChannelGroupNumber    ChannelGroupName      ChannelGroupDescription           ChannelName                   ChannelDescription              Unit     DataType    NumSamples
    __________________    ________________    ___________________________    _____________________    ______________________________________    _____    ________    __________

            1                "SawData"        "Circular Saw Measurements"    "Revolutions (1/min)"    "Rotational speed of the circular saw"    "rpm"    "Double"      47144   
            1                "SawData"        "Circular Saw Measurements"    "Current (A)"            "Current in the circular saw"             "A"      "Double"      47144