How to accurately measure rotation? 1

[ritchie888]

I need to know the type of component I should use to determine the rotation of a shaft. Basically, I'll be building a pendulum which will hang down at 0' (due to gravity) with an axle at the top of it where I'll also mount the sensor (basically I'll look like the face of a clock with only one arm that always points to 6o'clock, due to gravity as I say, it'll only need to move in 2D). If I was to push that pendulum in an anti-clockwise manner, I want to calculate the positive rotation angle as it moves, likewise the rotation angle will be negative when it passes the 0' point in the other direction.

I'd like to use a mechanical method, such as a rotary encoder, rather than optical methods which don't seem to be as applicable to my application.

My problem here is that I don't know what attributes of a rotary encoder I need. Being able to measure 360' would be a plus, although I don't expect the pendulum to do a full rotation, being able to measure at least every 1' is necessary, anything more accurate would be a plus, and I need the shaft to rotate freely, not to 'click' round like I've seen in my switches which come in the same physical package.

I've been looking at something like this:

http://uk.farnell.com/bourns/pec11-4220f-s0024/incremental-encoder/dp/1653381?Ntt=PEC11-4220F-S0024

Would that be viable?

Cheers!

 

[imcjoek]

Rotary encoder is tough to beat, but you still need some equipment to log/count its output. Also, you still have no idea what CPR you need.

Expanding on IFRs idea, you can use a motion-controller style stepper or servo motor to swing the IMU through a preprogrammed (and highly accurate if you do it right) motion profile. These are either really expensive or not expensive at all, relatively speaking, because you haven't really specified what cost you are shooting for either.