how to make RPM meter with labview ?

[Hutomo]

hello guys,

I want to measure the speed of my mini wind turbin.

so i use proximity sensor and converter from frequency to voltage.

And now i have the voltage output.

My Q is, how to calibrate or convert the voltage output into RPM using labview ??

Thanks 

[johnsold]

Hutomo,

Your question indiciates some misunderstanding or a language issue.

It appears that you have two components to the problem.

1. How to measure a voltage.

2. How to convert the voltage measurement to indicate RPM.

LabVIEW is a programming language and cannot by itself measure a voltage.  LabVIEW can easily control and communicate with a variety of devices which do measure voltage, from digital multimeters, to oscilloscopes, and to data acquisition cards, boards, or devices.

The calibration process depends on knowledge of your external circuitry. How many pulses does the proximity sensor produce for each revolution of the turbine? What is the relationship between frequency and voltage for the converter?  Once the voltage is measured and the data is present in LV as a number, you can apply the appropriate mathematical transformation to get the speed in RPM.  LV has all the tools to do the math.

Also, as this question is a more general LabVIEW question and not really a signal conditioning question, you would probably get more responses by posting on the LV Board.

Lynn

[Henrik_Volkers]

Looks like a hobby project.

A cheap way to measure RPM is the sound card of your PC but this involve that you have at least about 15 pulses per second (and max about 20k) . (you measure the each blade or n pulses per revolution and measure the frequency)

What is the RPM range you want to monitor?

To read a voltage you need an ADC hooked up to your PC. Best and easy working with LabVIEW is a NI DAQ device. Small budget parts are the USB 6009 (or myDAQ if you are still in school/education)

Or you use a multimeter with RS232 connection. That will involve more software for the communication (usually you will have to write that for the cheap handheld DMMs, but have a look at the LabVIEW driver database) and might have other pitfalls (auto shutdown of the DMM, run out of battery..)

For the calibration, you apply known frequencies(RPMs) to your sensor and measure the voltage. Depending on the voltage/Frequency(RPM) curve you get you apply a linear (or polynomial) fit .

All that is easy done in LabVIEW (in case of using a NI- DAQ device the driver software can already do that for you)

And guess what the sound card is good for if you don't have a (calibrated) signal generator or DAQ device with timer output ?

(Don't expect too much from a cheap soundcards (my guess is 0.5% to 1%) , but others have done tests about it you can find in the web)