Measureing frquency and vibration

Mecheng1

I have the Hitachi H48C three axis accelerometer and it seems to be pretty easy to measure G forces. Has anyone tried to use it to measure vibration, if so how can you get it to measure and record a frequency? Also is there a way to both record and plot data from the accelerometer.

JasonDorie

It depends on the frequency of the vibration you're trying to measure, since the accelerometer will read vibration up to 500Hz, it limits you to measuring vibrations of less than half that, and that's if you're sampling at the crest / trough of each.· You probably want to stick with frequencies of more like 1/4 the sample rate to get good measurements.

If you're looking at motor vibration, convert to RPM with:

RPM = Freq * 60 = 30,000rpm, then divide by the number of samples per wave you want (2 to 4)

Does that make sense?


The H48C is just a sensor, so it won't record/plot the data.· I've used the Parallax Oscilloscope to plot it, and used it to reduce vibration for imbalanced airplane propellers.

Jason
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Mecheng1

That sort of makes sense. I am actually trying to measure the disturbing frequency of a boat which is going to include the motor and up and down motion of the waves combined. I don't think it's going to be greater the 500Hz. What I'm not sure about is how to write the program to get it to output a frequency. Is there a sample code that I can look at somewhere, the only code I have seen outputs G's. Once I can get it to output a frequency than I can worry about recording it.