Testing Pivotal Frequency

Hello, I'm not really sure where to start with this one... I recently brought the missus a 'Pivotal Vibration Plate' (url for exact model below) which claims to produce frequencies from 14-40hz per second. Just out of interest I wanted to test this. How could I test Pivotal Frequency? I was thinking of perhaps using some form of accelerometer, along with the Arduino recording the data? Am I even close?

http://www.jtxfitness.com/jtx-6000-vibrating-exercise-plate.html

Appreciate the guidance...

  • use a stroboscope - A bright white LED switched on/OFF with an Arduino
  • open it and check the internals for the right wire
  • use a lamp and a photodetector and place some shutter on the device - then count the pulses
  • ...

An accelerometer will do the trick as well. Just display the waveform on your PC -- may not be trivial.

I measure LFN with an Arduino/PC system.

You should just be able to use a microphone and oscilloscope (or arduino oscilloscope) to see the vibrations.

14Hz is way below most microphones good sensitivity range and a plate that small won't act as a good loudspeaker for wavelengths of tens of metres. I think there'll be a lot of audio noise at higher frequencies from the motors and mechanics.

I'd place a strong magnet on the plate and hold a coil of wire over it attached to an oscilloscope - crude as a guitar pickup.

14Hz is way below most microphones good sensitivity range

I agree but you will still get something out of the microphone to measure. We are not looking to make an audio recording here just a measurement.

It seems possible to use a laser pointer, a mirror mounted to the base, and a photo resistor attached to the arduino to measure the vibrations. With the right alignment and distance, you could measure the frequency from the photo resisitor. I'm not sure how feasible this is given the specs of the arduino.