The TDMS data model automatically creates certain properties when some data types are written. However, in many cases you may want to create a property specific to your particular needs, such as UUT, serial number, and test temperature. This task can be accomplished using the TDMS Set Properties VI with which you can write properties at the file, group, or channel level, as shown in Figure 4.
The file level of a property determines which input terminals need to be wired. For example, to write a group property, only the Group Name terminal needs to be wired. To write a channel property, both the Group Name and Channel Name terminals should be wired. But, to write a file property, the Group Name and Channel Names terminals should be left unwired. These cases are illustrated in Figure 5.
Figure 4: Write custom properties at three different levels before writing data to the file.
With the TDMS Set Properties VI, you can specify an individual property by itself or specify many properties by using arrays. Figure 4 shows that we are specifying two properties at the file level (TestID and Plant). This could be expanded to specify many more properties by just increasing the size of the array. Arrays are not necessarily needed if only a single property is written, such as a serial number.
Property values can also be different data types. In Figure 4, string properties were written at the file and group level. But at the channel level, we write two numeric properties to specify the minimum and maximum temperature.
Figure 5 illustrates how you can use the TDMS Set Properties VI to save additional descriptive information at the file level. In this example the date and the user of the test are built into an array and then written as custom properties.
Figure 5. Use the Set Properties VI to save additional descriptive information at the file level.