I'm trying to determine the change in frequency with voltage of a coin vibration motor (https://solarbotics.com/product/vpm2/) using an oscilloscope. So far I have tried two different set ups.
Set up 1:
The coin vibration motor is being powered using a mosfet and an arduino to vary the voltage using PWM. I hooked up two probes to the oscilloscope, one on each of the motor's leads, and subtracted the two signals. The only signal that was picked up was the PWM.
Set up 2:
The coin vibration motor is hooked up to a power supply through a 1 ohm resistor. I used one probe from the oscilloscope to detect the voltage drop across the resistor. This set-up was one I found reading through previous replies to a similar question here. It didn't work, as the oscilloscope only showed what appeared to be noise signals.
I've read through other options such as using an accelerometer. Would something else besides an oscilloscope be a better option? Or is there a way to read the vibration using an oscilloscope and I just haven't got the right set up?