how to measure rpm

[Eluan]

I have an NI 9401, labview 8.6 and a 9172 chassis and I am trying to measure the rpm of my rotating shaft. The code I wrote works at low speeds but is not accurate at high speeds. Does anyone have a standard labview 8.6 code for obtaining the angular velocity of a rotating object?

[Zach J]

Hi Eluan,

What part of the code is inaccurate?  Is it the calculation or do you think you need to sample faster to gain more accurate measurements?  It is possible that there is noise in your data that you could average out to obtain more reliable measurements.  Is the measurement being taken with a specific type of device (eg: hall effect sensor, rvdt, encoder)?  There are a lot of different methods for measuring angular velocity of a rotating shaft, so please let us know what method you are using.  We will be better able to help you if we know a little bit more!

[Eluan]

I am using a quadrature encoder

[Eluan]

I am using a quadrature encoder and the code I wrote works well when I'm trying it at less than 80 rpm but I need it to work up till at least 800 rpm

[Zach J]

Hi Eluan,

What is your sample rate for the acquisition?  It sounds like you may not be sampling fast enough to keep up with the increased number of pulses generated in a given timeframe.  If you would like to post a screenshot of your code, I might be able to provide some suggestions for ensuring you do not miss any pulses.