JAZZ PLC RPM sensing issue

[Mingyu]

I have a JAZZ PLC(JZ20-UA24) for our mini turbine application, we were trying to measure the RPM using its high-speed input with the proximity sensor and one magnet, but the problem is the result is too coarse with a 60rpm step.

Is there any other method to calculate the rpm based on the high-speed input to get a better accuracy?

Is the JAZZ plc able to record the time between two pulses to calculate the RPM?

Thank you!

[Joe Tauser]

If you're getting one pulse per revolution on a 60 RPM shaft you really don't need a high speed input.  You're getting a pulse every one second.

You can set up a self-resetting 0.01 second timer as a pulse generator and just count the timer pulses between the proximity sensor pulses.  You could also add more magnets around the shaft to get more pulses per revolution.   Use your imagination.

What kind of resolution are you looking for?

Joe T.

[Mingyu]

Thanks Joe, the shaft rpm range is from 1200 to 2700 and I am looking for a 10rpm resolution. I tried using HSC to count pulses every second and then times 60 to get the RPM,  but the result is a bit bouncing and the resolution is 60, which is not really good. I was thinking to count period time between pulses. but the timer resolution is 10ms which is not accurate enough. i am wondering if there is any other approach to calculating the RPM in JAZZ PLC.  

[Joe Tauser]

Not in a Jazz.  There is a function in the Vision that may be helpful, but that's not your question.

The problem is you're short on pulses/rev to get good resolution. Does your physical setup allow you to get an encoder with a rubber wheel on it that can ride on the shaft or otherwise couple to it?

Joe T.