I have tested the Damian's advice. The system work fine but only in low speed. (about 500 pulse for minute).
When i go in hight speed, i lose some pulse, i don't see light up of the led in input card!
Now if i have 20 pulse for minute there is NO problem also for a normal input, because the response time is 10ms on all inputs: 1000ms / 20pulse = 1 pulse
every 50ms. But the problem is: how long a pulse when the wheel run in hight speed? About 0,1mS. This time is the problem.
If i have set the input as HSC i have Minimum pulse width = 80µs. For a normal input i don't know!!!
I have contact unitronics support that advice me to use Immediate Read Physical Input. In this moment i can not try because i'm far from the plant, but
i think that also this solution NO solve problem because Immediate Read Physical Input function is called every plc scan....about 2 ms.
What is your opinion? Is there other way?