Read Input Cicle - M340

[ndelucca]

Hi everyone, i have a situation with a Modicon M340 PLC.
I need to measure an external magnitude with a digital input. I'll be receiving pulses in that digital input, the more pulses i get in a period of time, the biger the value.
The problem i've encountered is that i need to sample the input at 1ms. The PLC cicle is rounding the 10ms, so its too slow for regular programing.
I guess what i'm asking is basically if i could force the plc to read a particular input separately of the regular scan cicle, at least at a rate 10 times faster.

I hope i've made myself clear, otherwise i'll explain again.

Thanks!.

 

[robertkjonesjr]

Maybe something like - high speed counter module?

 

[ndelucca]

Thanks robert, i've actually seen that module before, but i discarted a hardware solution because i have a full 12 slot rack, with no posibility of expanding it at the present moment.
I'm looking for a programming solution, maybe by using a FAST task (wich i'm not so sure how it works, i've always worked with the MAST task only) or something like that.

 

[Lare]

You need to congigurate digital input to Fast period first (they are at 8 inputs group on module)
Then program fast task and use these inputs on fast task. Anyway not sure if you can even go to 1ms period with normal digital input card.

 

[danatomega]

If you have an analog input available you could use a frequency to voltage convertor which is available fro Red-Lion controls amongst others ...