Edge Counting

You can take edge counting measurements with the NI-9361.

The counter counts the number of active edges on a signal. The NI-9361 returns the current count value when the counter is read. The following figure shows an example of edge counting.

Figure 8. Edge Counting

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Channel Settings

You can configure the following counter properties:
  • Input terminal of the signal-to-measure.
  • The initial value of the count.
  • The active edge, rising or falling, that is counted.
  • Count direction to increment or decrement the counter on each edge—You can set this property to:
    • Count Up
    • Count Down
    • Externally Controlled
    Note If you select Externally Controlled, the NI-9361 monitors a hardware signal to determine the count direction. When the signal is high, the counter counts up; when the signal is low, the counter counts down. You can set which signal to monitor.
  • Counter Reset—You can configure the counter to reset the count to a specific value in response to a hardware signal using the following Reset Trigger properties:
    • Enable or disable the Reset Trigger feature.
    • Input terminal of the signal to be used as the Reset Trigger.
    • Reset Trigger active edge to select the rising or falling edge of the signal to trigger a reset.
    • The reset value to change the count value to in response to the Reset Trigger.
  • Count Edges Pause Trigger—You can configure the counter to pause counting based on a hardware signal using the following properties:
    • Enable or disable the Count Edges Pause Trigger feature.
    • Input terminal of the signal to be used as the Count Edges Pause Trigger.
    • Count Edges Pause Trigger level to select pause counting when the signal is high or low.

The following figure shows an example of a count edge measurement using the Reset Trigger with the initial value of the count value set to 6, Reset Trigger active edge set to rising edge, and the reset value set to 3.

Figure 9. Reset Trigger

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The following figure shows an example of edge counting with Count Edges Pause Trigger level set to high.

Figure 10. Count Edges Pause Trigger

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Trigger Settings

Counter Arm—You can control when the counter starts counting through the counter arm control. The counter waits for the active edge on the signal-to-measure after it is armed, and counts on every active edge on the signal-to-measure. Refer to your software documentation for more information on arming the counter.