Calculate RPM

[Husanto 0]

Hi All, I want to calculate RPM from motor. I use proximity for read the input signal with CPM2A. Can any body tell me how to calculate RPM with this system using CPM2A?? 1 pulse is 1 rotation. Thanks Husanto

[lostcontrol 23]

Have a look at using the HSC & PRV instruction, this will give you the frequency of the signal, which you can then convert to RPM...

[Husanto 0]

But I think we can use PRV2 and it doesn't have in CPM2A. Maybe you have algorithm for calculate the RPM?? Thanks

[pfort 20]

PRV is available in CPM2. If you want to calculate RPM, i suggest you decide a "sample time". Suppose it is 1 sec, you multiply the pulse you got in last sec by 60 then you have the RPM. If it is 5 sec., you multiply by 12. Etc...

[Husanto 0]

But it very slowly.. I want to display it on touchscreen. How about if the RPM under 60 RPM??

[Sleepy Wombat 27]

What is the highest RPM you want to measure ? You could measure the time between pulses and correlate that to an RPM with some simple math.. you can work that out as I don;t believe in spoon feeding. This method has speed limitations due to response times PLC scan etc. And another way to increse the accuracy is to have more sensing points... ie more then 1 pulse per revolution.. Why do you think that incremental encoders have higher resolutions ?... in your case if you had four teeth then this would be a minimum of 15 RPM...

[Husanto 0]

the highest RPM is 160 RPM and the minimum is 60RPM. How do you think??

[pfort 20]

In the past a had a DC motor 0-200RPM that i wanted to monitor the RPM with only a sensor.(Only 1 input available on PLC for this) Before i work on it it already had a sensor but with only 1 sensing per revolution. I wanted more precision because it was an auger. I changed the reed switch that was there for inductive sensor. And instead of the magnet that was there, i made something that had 6 part of metal on his 360 degree. So the sensor is "ON" 6 time per turn. Then with some code you easily can convert it to RPM. With a base of time of 10 sec it is easy, 1 pulse per 10 sec = 1RPM.