need to read pulse in micro second

[harrydeharry]

Dear All,
We have to read the time gap of two rising pulse which is in micro second how can we do it in plc.(any plc)
thanks in advance.

 

[rdrast]

You don't.
PLC's as a general rule don't have any input devices that can respond in microseconds.

I suppose maybe, you can find some type of extremely high speed counter to do this, but it's still unlikely.

You will be looking at extremely fast motion controllers, or more likely, dedicated hardware for this. You might be able to do it with an Arduino, or similar programmable system-on-a-chip.

 

[Ken Roach]

I am working on a project right now where I have to compare two pulses that arrive just a few microseconds from one another. About 50 microseconds is the difference between an overload signal and an underload signal on a tiny solenoid driver circuit.

I'm using interrupts on an Arduino-based microcontroller (a Pololu A-Star 32U4) and communicating with my main system over Modbus RTU protocol. Everything else on the machine is automated by ControlLogix, but this specific super-fast function needed a dedicated microcontroller.

 

[MartB]

If you're working with Allen Bradley, I've used 1756-IB16IF cards for microsecond measurements before. However, they are better suited to applications with pulses of 10 microseconds or longer.

From the manual: "The 1756-IB16IF fast input module can be used to detect or latch short duration pulses. The module can detect incoming pulses with a duration as short as 10 μs if the frequency is under 4 kHz (period of 250 μs)."

 

[just the cowboy]

automation direct

depending on how many micro sec you are looking at automation direct has a CTRIO high speed counter card that has the function you are looking for setup in it.

 

[shooter]

Yes arduino could do this, and also control more complex things.
On the other maybe a simple 556 can help you out.
You can have a converter from Pulses to Volts.
If you have analog inputs use them with this 555, if you dont have analog inputs make a PWM signal long enough to cope with the slow speed of the PLC.

 

[JRW]

Harry
I'm doing it with the Siemens ET200SP TM Timer module
You don't need a motion controller
PM me if you need details