Use the Start Trigger signal to begin a measurement acquisition. A measurement acquisition consists of one or more samples. If you do not use triggers, begin a measurement with a software command. Once the acquisition begins, configure the acquisition to stop in one of the following ways:

  • When a certain number of points has been sampled (in finite mode)
  • After a hardware reference trigger (in finite mode)
  • With a software command (in continuous mode)

An acquisition that uses a start trigger (but not a reference trigger) is sometimes referred to as a post triggered acquisition. That is, samples are measured only after the trigger.

When you are using an internal sample clock, you can specify a default delay from the start trigger to the first sample.

The name of terminal using the Start Trigger task can be queried using the Start Trigger Terminal Property.

Using a Digital Source

To use the Start Trigger signal with a digital source, specify a source and a rising or falling edge. Use the following signals as the source:

  • Any PFI terminal
  • Counter n Internal Output

The source also can be one of several other internal signals on your TestScale backplane. Refer to the Device Routing in MAX topic in the NI-DAQmx Help or the LabVIEW Help for more information.

Using an Analog Source

Some TestScale modules can generate a trigger based on an analog signal. In NI-DAQmx, this is called the Analog Comparison Event. When you use an analog trigger source for StartTrigger, the acquisition begins on the first rising edge of the Analog Comparison Event signal. For digital input timing, the analog trigger circuit must be configured by a simultaneously running analog input task.

Note Depending on the TestScale module capabilities, you may need two modules to utilize analog triggering.

Routing Start Trigger to an Output Terminal

You can route the Start Trigger signal to any output PFI terminal. The output is an active high pulse.