Trigger and Gate

• Threshold—

  Uses a threshold to indicate when to start triggering.

  • Start sense—

    Specifies on what edge of the signal to start taking samples. The options are Rising edge, Rising or Falling edge, or Falling edge. This option is available only when you select Threshold.

  • Start level—

    Amplitude that the signal must cross in the Start sense direction before the Express VI starts taking samples. The default is 0. This option is available only when you select Threshold.

  • Pre samples—

    Specifies the number of samples that occur before the start trigger to return. The default is 0. This option is available only when you select Threshold.

• Immediate—

  Begins the triggering immediately. The start of the signal is the start trigger.

• Number of samples—

  Ends the triggering when the Express VI collects Samples.

  • Samples—

    Specifies the number of samples to collect before stopping the trigger. The default is 1000.

• Threshold—

  Uses a threshold to indicate when to start triggering.

  • Stop sense—

    Specifies on what edge of the signal to stop taking samples. The options are Rising edge, Rising or Falling edge, or Falling edge. This option is available only when you select Threshold.

  • Stop level—

    Amplitude that the signal must cross in the Stop sense direction before the Express VI stops taking samples. The default is 0. This option is available only when you select Threshold.

• Trigger channel—

  Specifies the channel to use if the dynamic data type input contains multiple signals. The default is 0.

• Reset after each trigger found—

  Resets the trigger conditions after finding each trigger. When you select this option, the Trigger and Gate Express VI does not buffer data with each iteration of a loop. Select this checkbox when you have a new data set for each iteration and you want to find data related only to the first trigger point. Deselect this checkbox when you want to pass only one set of data into a loop and then call the Trigger and Gate Express VI in a loop to get all the triggers in the data.

  Note When you do not select this option, the Trigger and Gate Express VI buffers data. In this case, if the Trigger and Gate Express VI is called in a loop, it can start a backlog of data if there is new data for each loop (because one set of data can contain several trigger points). Because there is no reset, it buffers all the data from each loop so that it can find all the triggers, but all the triggers might not be found.
• Remain triggered after trigger found—

  Remains triggered after finding a trigger. This option is available only when you select the Threshold option in the Start Trigger section.

• Hysteresis—

  Specifies the amount above and below Start level or Stop level through which Signals must pass before a trigger level crossing is detected. The default is 0.

  Use trigger hysteresis to prevent noise from causing a false trigger. For a rising edge Start sense or Stop sense, the signal must pass below Start level or Stop level minus Hysteresis before detecting a trigger level crossing. For a falling edge Start sense or Stop sense, the signal must pass above Start level or Stop level plus Hysteresis before detecting a trigger level crossing.

• Automatic number of samples—

  Specifies that the Express VI returns the portion of the signal that matches the trigger criteria.

• Number of output samples—

  Specifies the number of samples to include in each output segment. This option is available only if the Automatic number of samples checkbox does not contain a checkmark.

If you wire data to the Express VI and run it, Input Signal displays real data. If you close and reopen the Express VI, Input Signal displays sample data until you run the Express VI again.

• Number of points in the data—

  Specifies the number of points in the data. The default is 4400.

If you wire data to the Express VI and run the VI, Results Preview displays real data. If you close and reopen the Express VI, Results Preview displays sample data until you run the VI again. If the cutoff frequency values are invalid, Results Preview does not display valid data.