My college team and I are trying to develop small AUVs whose thrusters are much smaller than commercially available. We have a prototype ready and would like to test the RPM of the motor underwater for various loads. Is there any method to measure the RPM/torque of small motors(small shafts)?
There are several methods for measuring motor torque and/or RPM, but the most appropriate one(s) will depend on the context. To start with:
what kind of motors are you using? (brushed DC are easy to measure the current of, which should be approximately linear to torque, but other motor types are a bit more complex)
what do you mean by “various loads”?
will you be testing with a propeller attached, or are you able to test without stirring up the water?
do you have a rough idea of the expected RPMs? (it may be possible to measure with a phone camera, either from above looking at a line on the shaft, or from the side through a clear container/tank wall or just in with the motor with a water-proof phone, or alternatively you may want/need to measure the rotations with a magnet and sensor)
