Calculate RPM from analog inductive sensor

[Stuart.Parkinson]

Maurlind, I cannot open your tdm files - they are corrupt or incomplete! However the signal looks clean enough to be able to extract the pulse period easily enough. Have you tried the Pulse Meas vi from Signal Processing->Wfm Measure?

[maurlind]

Hi!

I have a cDAQ 9178 with an analog  input moduel NI 9201.  

I have also tried the pulse measurment vi, but it didn't gave me any right frequency numbers, maybe I'm using it in the wrong way. But it shouldn't be any harder than wiering my signal to the pulse measurment vi and then extract the period.

Best regards Maurlind!

[Hooovahh]

Just an FYI, that 8 slot chassis has 4 counter timers that can be used between I/O.  Two of them can be routed to the front two BNC connectors and accessed without needing any cards.  Here is an example where I used it to perform a frequency sweep using those two front BNC connectors.

https://decibel.ni.com/content/docs/DOC-32352

[maurlind]

Hi!

Hooovahh, I tried your first program but it was started with 2499 pulses seen, and when I wass running my shaft nothing really changed, the pulses seen went from 2499 to 2498 , just changeing from those two values. 

And with the BNC thing seems harder two use than just the basic analog voltage input from my module. 

Surley there must be a way to calculate the pulses and get thier frequency?

I dont really understand how counters work or how I do to set them up in my cDAQ 9178, it seems that Labview can't find them when i browse form them in Daqmx physical channel.

Best regards Maurlind!

[maurlind]

Hi!

Could it be so that my rate and number of samples is the key to get the pulse measurement and tone measurement vi to work?

I noticed when a have 1000 samples and 500samples/second it would start giving me the rpm values, but they were only updating with 60rpm each time I increased the motor speed.

For an example, I have a 50Hz Ac-motor and I can adjust the frequency to runt the motor at different speed. 2Hz gave me 60rpm, and 4Hz gave 120rpm and so on, setting the frequency to 3Hz the rpm value would then jump between 60 and 120 which seems strange, note that the maxium rpm is 2875rpm.

My question is, does this have something to do with the sample rate and number of samples acquired in my daq? If not how can I make this work properly?

Best regards Maurlind