Period measurment for RPM?

[dontknowwhatimdoing]

I'm working on a project and have had no previous experience with LabVIEW, and I could really use some help. The project is using a proximity sensor to measure the RPM of a motor shaft (the proximity sensor will be activated by a bolt in the shaft). Basically, I want to make a program to measure the period of the digital signal from the proximity sensor and use that to calculate RPM.

I have attached what I have so far for the program, but I'm not getting any data when I run it. I'm using an NI myDAQ. I've tested the circuit using the test panels in the device manager and I know the board is getting a signal, but I don't know how to troubleshoot it or where to go from here.

Any help is greatly appreciated.

[chuggins1434]

Hello,

Is this for a class (you're married to LabVIEW for the processing) or is it another type of project?   ...if it's for a LabVIEW class then I'll probably let others chime in... if you're open to other options then I can probably lead you down another path.

Regards,

C

[santo_13]

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@dontknowwhatimdoing wrote:

I'm working on a project and have had no previous experience with LabVIEW, and I could really use some help. The project is using a proximity sensor to measure the RPM of a motor shaft (the proximity sensor will be activated by a bolt in the shaft). Basically, I want to make a program to measure the period of the digital signal from the proximity sensor and use that to calculate RPM.

I have attached what I have so far for the program, but I'm not getting any data when I run it. I'm using an NI myDAQ. I've tested the circuit using the test panels in the device manager and I know the board is getting a signal, but I don't know how to troubleshoot it or where to go from here.

Any help is greatly appreciated.

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Please share the VI in an older version (at least 2019) as most of the users are still not up to 2022.

You can do this by, File -> Save for Previous version

[RTSLVU]

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@dontknowwhatimdoing wrote:

I'm working on a project and have had no previous experience with LabVIEW, and I could really use some help. The project is using a proximity sensor to measure the RPM of a motor shaft (the proximity sensor will be activated by a bolt in the shaft). Basically, I want to make a program to measure the period of the digital signal from the proximity sensor and use that to calculate RPM.

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I can't look at your code because it's too new of a LabVIEW version but...

I think you want to measure frequency using a counter input not period of each revolution pulse.

BTW: Save your VI for LabVIEW 2021 or older for more responses as many of us are frozen on LV 2021 due to the new ultra expensive yearly subscription for the rest of your life model NI has chosen. 

[crossrulz]

I just saved the VI to LabVIEW 8.0 (I dare somebody to honestly say they can't open it).

So what periods are we expecting here?

[dontknowwhatimdoing]

Yes, this is for a class and I'm stuck with LabVIEW.

[dontknowwhatimdoing]

First, thanks to everyone for the responses.

The max RPM is about 1800, minimum is unknown at this point but I think it will be around 1200. I'm expecting the max period to be 33.33ms.

I messed around some more and now have a working program using a simple push button circuit. Uploaded it using an older LabVIEW. Eventually the Y axis of the graph will measure a load cell voltage, but I don't have the load cell right now so I just used a random number generator for the sake of making the graph.

Now my problem figuring out how to wire up and get a signal from the proximity sensor. I do have an external power supply for the sensor. It will be set at 18V to power both the prox. sensor and the load cell. I was messing around with it today but haven't been able to get a signal to my program.

Any help would be appreciated, thank you in advance.

[RTSLVU]

I still question why you are measuring the period? 

From the description of your setup (the proximity sensor will be activated by a bolt in the shaft) you are going to receive one "pulse" per revolution.

So a frequency counter would directly measure Revolutions Per Second and converting that to RPM is simple math 

[dontknowwhatimdoing]

I used the period just because that was the input I got to work. I tried frequency, but kept getting errors in the VI. I'm completely new to LabVIEW, so I probably missed something or had some setting wrong. The conversion from period to frequency wasn't difficult so I was just going to stick with what is working for now. You are correct about one pulse per revolution.