maxPAC Hardware Reference Guide
Metso Automation MAX Controls Inc. • 277596 •
9-2
Jumper Installed Not Installed
W1A - 16A 24 V 48V
This microprocessor-based module supports up to eight pulse input channels.
Each channel can be independently configured for both function type and
debounce time. The functions supported are:
Mode 1 – Frequency Input
Frequency in counts per second in input1. Input 2 is not used. The
Pulse I/O Buffer in DPU4E supports the following timebase mode
selections for frequency measurement: 20 msecs, 50 msecs, 100
msecs, 250 msecs, 500 msecs, and 1 second. For the selected
timebase, the Pulse I/O module measures frequency for the
specified duration and normalizes each measurement to cycles per
second. The measurement is updated at the end of each interval
and the counts read by the DPU when the module is scanned
represent the average of the last four measurements in
cycles/second. The scan rate of the DPU is asynchronous from
the scan rate by the module. The accuracy of the frequency
measurement is +/-1 count for the one-second timebase. The
accuracy for the other timebases is approximately the normalizing
multiplier divided by 4. Thus for the shortest timebase (20 msecs),
the accuracy is reduced to approximately +/-12 counts.
In applications requiring fast frequecy measurements, a period
measurement (mode 7) can also be used to measure frequency.
Since each count in the period measurement corresponds to 0.5
microseconds, the inverse of the period will yield a fast frequency
measurement with an accuracy of 0.1% for a 2000Hz input and
0.25% for a 5000Hz.
Mode 2– Simple Event Counter (default configuration)
32 bit accumulation of OFF-to-ON transitions in input1. Input2
provides an external accumulator reset.
Mode 3 – Up/Down Event Counter
Net counts of OFF to ON transitions in input1 and input2. Input1
counts up and input2 counts down.
Mode 4 – On-Time Timer
The timebase frequency (0.5 usec/count) is counted while input1 =
ON. Input 2 provides an external reset.
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