Web Interface
The pulse frequency computed channel is designed to measure pulse frequencies, primarily in conjunction with Digital Input Channels. The system scans the logical input channel for falling edge and rising edge transitions. The pulse period is updated based on the time period between rising-to-rising edges and falling-to-falling edges.
NOTE
The pulse counter frequency output is also update if the time period since the last set of edges exceeds the current output. This results in improved results as the pulse trains slows or stops.
Specify the Output rate factor, which is the down sample factor that determines the output channel sample rate. For example, for an input channel with a sample rate of 10000 Hz and an Output rate factor of 1000, the output channel sample rate is 10 Hz. The value must be an integer of 10 or greater.
Specify the Output scale factor, which converts the output data from Hz to the desired physical units. The Output scale factor cannot be zero.
Specify the Minimum output frequency, which is the output value if a new pulse is not detected within the specified period. The value is output until the detected pulse period is less than the specified period. For example, if the input channel is a 50 Hz pulse train that suddenly stops, the pulse counter output remains at 50 Hz until a new pulse frequency is detected or until the specified period has elapsed. This value is also the initial channel output until the first pulse is detected.
NOTE
The accuracy of the pulse frequency measurements depends on only the sample rate of the input channel. For example, using an input channel sampled at 2000 Hz provides 1% accuracy of a 20-Hz pulse signal and 0.1% of a 2-Hz pulse signal. As a general rule, the input sample rate should be 100 times the maximum expected pulse frequency to provide 1% or better accuracy of the entire pulse frequency range.