Dear All,
I read in this forum that to select a counter module we should know the following things.
- The maximum flow rate through your flow meter
- The maximum scan time of your PLC
- The maximum input frequency of your hardware input
Once you work out your maximum flow rate, you can calculate how many pulses per second you will be getting on the input. Then you can calculate the time between pulses.
If the time between pulses is less than (or close to) your maximum PLC scantime, then you will need a high speed counter.
If the number of pulses per second is larger than (or close to) your maximum input frequency of your hardware input, then again, you will need a high speed counter.
If neither of those cases are true, then you do not need a high speed counter and can do it using normal counter logic in the PLC.
Can anybody give me an example to understand completely the aforementioned points?
How do I know how many pulses per second I will be getting on the PLC input?Calculate the time between the pulses. How?
Period of one complete cycle minus the pulse width time
If the number of pulses per second is larger than (or close to) your maximum input frequency of your hardware input, then again, you will need a high speed counter.
What is the maximum input frequency of the hardware?
I read in this forum that to select a counter module we should know the following things.
- The maximum flow rate through your flow meter
- The maximum scan time of your PLC
- The maximum input frequency of your hardware input
Once you work out your maximum flow rate, you can calculate how many pulses per second you will be getting on the input. Then you can calculate the time between pulses.
If the time between pulses is less than (or close to) your maximum PLC scantime, then you will need a high speed counter.
If the number of pulses per second is larger than (or close to) your maximum input frequency of your hardware input, then again, you will need a high speed counter.
If neither of those cases are true, then you do not need a high speed counter and can do it using normal counter logic in the PLC.
Can anybody give me an example to understand completely the aforementioned points?
How do I know how many pulses per second I will be getting on the PLC input?Calculate the time between the pulses. How?
Period of one complete cycle minus the pulse width time
If the number of pulses per second is larger than (or close to) your maximum input frequency of your hardware input, then again, you will need a high speed counter.
What is the maximum input frequency of the hardware?