Low RPM measurements

[MogaRaghu]

I have attached a VI that is for measuring rpms from 100 to 6000 using a photosensor that gives 1 pulse/rev.

I am not happy with the setup as I had to resort to some exotic case structures to handle the cases where the rpm was below the minimum threshold ; when there was no rpm and the like. Without these case structures, the measurement was quite crazy with lots of zero readings and very large readings in between correct readings. Now anyway it is just OK for speeds above 1000 rpm.

Question is : Is there any other better methodology to measure rpm? ( Sorry - but due to practical reasons the pulse rate cannot be increased beyond 1 pulse / rev.)

Thanks

Raghunathan

[bushman]

You are going to have many problems at sucha low sampling rate.
For a dependable system you have to satisfy Nyquist Theorum.
Without the proper sampling rate you can't resolve a number properly, you get aliasing and many other challenges.

[MogaRaghu]

" You are going to have many problems at sucha low sampling rate."

Yes I know the issue here. But with just one pulse per revolution, I do have a problem. Even at 100 rpm the frequency of the input from the sensor is just 1.7 Hz and the period around 590 ms. So I have to neccasarily run the timed loop weel above this limit - and there in lies the headache.

Raghunathan

[Jeremy_L]

You may find more (and possibly better) help if you post this question in the LabVIEW Forum. or the DAQ Forum