Author Topic: PULSEFREQUENCY problems  (Read 9847 times)

nc5p

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PULSEFREQUENCY problems
« on: December 21, 2005, 01:02:19 PM »
How long does the PULSEFREQUENCY need to measure frequency?  I am having trouble executing it within a sequence, even with 4 second clocks being used.  It works fine if I just call it outside the sequence.  It really messes up the sequence counter whenever this function is called.  What I am trying to do is mux more than two flow sensors (5hz to 120hz signals) into the two pulse inputs, turning them on and off externally, then reading them sequentually.  It just won't work this way.  I need a suggestion on a workaround.

Thanks,

Doug

support

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Re:PULSEFREQUENCY problems
« Reply #1 on: December 21, 2005, 04:22:30 PM »
The pulsefrequency only needs the period between two rising edges to capture the correct measurement. So if you have continous pulses of 5hz feeding to the input it should be able to capture the pulse frequency every 0.2s and store the result internally. The result will be returned when it is being called by the PULSEFREQUENCY function.  

But if you have only a single one-shot pulse then multiplexing it may be more complicated since to the CPU it only measures the time between the current rising edge and the last rising edge and it  cannot be aware that you have "changed horse" in between.
« Last Edit: December 21, 2005, 04:24:10 PM by support »
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