# Question regarding rotational measurements

by bravo151515
Tags: accelerometer, measurements, rotation about axis, rotational
 P: 2 Hi, This isn't my field at all so please excuse my ignorance. Let's say I have a pipe positioned at 30 degrees to the horizontal and an inclinometer attached to the pipe in a vertical position. Now I rotate the pipe some amount about it's long axis. The inclinometer reads 15 (or whatever) degrees of rotation. How would you determine how much the pipe actually rotated? Thanks. I hope I made myself clear. Let me know if I haven't.
 Homework Sci Advisor HW Helper Thanks ∞ PF Gold P: 11,070 Welcome to PF; If you rotated the pipe about it's long axis, then it's actual inclination (to the horizontal) has not changed. How the inclinometer measures depends on the details of how it is attached - I take it this is a digital inclinometer? If I am reading this right, the inclinometer is attached in such a way that rotating the pipe does not make a simple rotation of the meter. I'd hazard that the device will measure the component of the rotation in the plane of the meter. If you used a pendulum incinometer, it would be fairly plain. It is easier to read the rotation of a pipe held at an incline by fitting a collar and/or sleeve - you can make it out of stiff paper - mark the sleeve in degrees, and mark a reference on the pipe. Use a plumb to make sure the 0 mark on the sleeve is "down" (or fix the sleeve to something i.e. the ground.).
 P: 2 Thanks for the reply, It is a digital inclinometer and it is attached in a vertical position perpedicular to the long axis of the pipe. It appears that the the amount of rotation of the pipe would equal the readout on the inclinometer. However, I was under the impression that this would only be exactly the same if the pipe was horizontal to the ground? Since it is at an angle, would there not be some amount of deviation? I also have a protractor with a plumb line down that can be attached via a pin through the side of the pipe. Do the 2 devices work on different principles? Would you recommend the protractor over the digital inclinometer? Thanks again!
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## Question regarding rotational measurements

The advantage of the protractor is that you can see how it works.
There are lots of ways to measure inclination - you don't have a little protractor in your head to tell how far you are tilted do you? The digital things are black boxes - I don't want to second guess what the manufacturer did: the second I do it will turn out yours is the exception ;)

You can test the accuracy of the inclinometer you use by rotating it a known angle and comparing with the reading. I don't imagine the tilt angle will have much effect on the incline angle the way you are using it.

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