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I have a 24VDC flow meter that outputs from 1.7Hz to 55.5Hz and is NPN. This is obviously not an HSC but rather a low speed device, will I have to treat it as an HSC in order to use this with a V570-57-T20B and V200-18-E1B? It will have its signal wire in position I0 and that block is wired for NPN inputs. I have base programs for HSC flow meter applications, but not this.

Any guidance will be greatly appreciated.


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My advice is ot define 1.25 ms interrupt subroutine, to read immediatelly there I0 and ot count both rising edges of it and interrupts. Once pre second (800 interrupts) you you will get the result in Hz. Maybe for better resolution you need to measure it once per more than one second.

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Use the function "Immediate Read Input"

Read the help file on immediate read. If you don't interupt the PLC when a pulse comes in, you could miss pulses during the scan time.

There is a cost to using the interrupts, it will slow down the program, but if you need it, you do it.

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