Flow meter input

Hi

Struggling with the programming of a flow meter input to PLC. I have a device that sends out a pulse for every ml going through. im not interested in what the flow rate is but more to ensure that something is going through the flowmeter (flow checker). I normally connect the device to another device which then has a relay ouput and I use this pulse to the PLC. now I wish to do away with this middle device but the plc does not see any pulse.

need some help. the device operates as a 3 wire device where by 2 are for power and 1 is signal. it is connected as I have said. I think I might have to use a HSC but don't where to start

You could use a High Speed Counter. Simply enable it in The device Configuration as a Single Phase Counter.

Otherwise you could generate a Interupt on a rissing edge of an Input, and every time you get a pulse ie. OB40 is called. It depends on how often you get the pulses. It dosn't give sense if you interupt your normal running program every ie. 2 ms.

Andy Moods

..I think I might have to use a HSC but don't where to start

Andy,

The HSC (high speed counter) can be used as a counter or to give "frequency" feedback. It is the frequency feedback that I think you need. the HSC in frequency mode has the potential  of saving you from a lot of coding.

PLEASE do make note of what our friend huggy_d1 has said. many people are having problems with this.

I hope to put your attention to a file called "Quick & Dirty_HSC for frequency indicator.pdf". This file can be seen in two threads. Please read through the PDF first and then work through both of the threads.. taking from it what you need.

[LINK1]

[LINK2]

If any questions.. do not hesitate to ask.
I am sure our resident expert(s) will be able to help.

Greetings.
w

Thanks guys. used the frequency option and it has worked out for me as the best solution. but part of the answer was also in the wiring. the flow checker was in the NPN orientation and I just used a pull up resistor to sort out picking up changes at the input as well.

thanks again