Configuring a Counter to Measure Pulse Width (Scan Interface)

CompactRIO Scan Interface

Configuring a Counter to Measure Pulse Width (Scan Interface)

You can configure a digital input channel as a counter to measure the pulse width of a signal connected to the channel. The counter returns data in µs. You can configure the following options for a pulse-width measurement counter.

Configuring the Input Filter

You can add an input filter to all input channels of the module. A filter removes noise, glitches, and spikes on inputs by rejecting signals with periods shorter than the specified length. You can select one of the following options.

  • Disabled—The hardware synchronizes the digital inputs using a 4 MHz timebase. Pulses longer than 250 ns are always detected. Pulses shorter than 250 ns may be rejected.
  • 1 µs—Pulses shorter than 1 µs are rejected. Pulses between 1 µs and 2 µs are sometimes detected. Pulses longer than 2 µs are always detected.
  • 16 µs—Pulses shorter than 16 µs are rejected. Pulses between 16 µs and 32 µs are sometimes detected. Pulses longer than 32 µs are always detected.
  • 256 µs—Pulses shorter than 256 µs are rejected. Pulses between 256 µs and 512 µs are sometimes detected. Pulses longer than 512 µs are always detected.
  • 4096 µs—Pulses shorter than 4096 µs are rejected. Pulses between 4096 µs and 8192 µs are sometimes detected. Pulses longer than 8192 µs are always detected.

Selecting the Measurement Type

  • High Pulse—The counter returns the time that the connected signal is high.
  • Low Pulse—The counter returns the time that the connected signal is low.
  • Most Recent—The counter returns the lengths of the most recent high and low pulses.