turning sensor?

Question

What would be a cheap solution for measuring turning with response time in ms (is a potentiometer fast enough)? What about a variable capacitor, can anyone point me to a site with schematics?

Thanks

The "sensor" should measure the angle at which a shaft is turned (about 10 measurements per second). The shaft will not rotate faster than 1 turn per second. The shaft can turn 180 degrees to the left or to the right from its original angle.
The torque for turning the angle could probably turn a variable capacitor. I really dont know much about electronics, so I would be very grateful if you could provide links to the sites with more info and specs. If I use a potentiometer should I paralel it to a resistor and a battery and measure the voltage on the resistor, which I will try to then channel into a paralel port on a computer.

Thanks to all answerers

Oops I made a mistake of course I meant to connect the resistor and the potentiometer in series.

Answer 1

EDIT: Note additional comment.

Whether you can use a potentiometer depends on the torque availble to turn the shaft. I would say that in most cases a potentiometer would not react fast enough. A variable capacitor could work if you could make it small enough and with low friction. It would help if you gave more information on what exactly you want to measure.


EDIT: ADDED COMMENT:

After reading your additional explanation, a potentiometer would be the cheapest and easiest solution. Be aware that most single-turn pots do not cover a full 360º; if you really need ±180º rotation, you should get a multi-turn pot. They are much more expensive, but they are also much more precise and repeatable, and also would have much better durability than a carbon-composition or wirewound pot.

Answer 2

There are some inexpensive sensors that measure the position of a magnet. I believe they are used for compasses on cars, but they have about a 5ms response time.

I saw a chip once (Q-sensor?) that would measure the difference in capacitance. You could put two plates within close proximity of eachother and monitor the capacitance, but I don't know if they would have the range you are looking for.

Potentiometers work, but if you have a lot of cycles, they can wear out or the contacts can become contaminated.

Optical encoder potentiometers are becoming common. They usually have about 200 counts per revolution.

I think there is still room for development on a fast, accurate, durable and cheap rotary measurement device.

Answer 3

Depending on the accuracy of the measurement you could use a metal detector and a sprocket, the metal detector setup so it will see each tooth as it passes by and count them digitally, once you know the number of teeth on the sprocket you know the angle it turned. To get more accuracy, get a larger sprocket and make sure you can count high enough.

This type of measuring is used in ABS systems, take care it's likely to be patented.

Answer 4

this depends on many factors such as whether it is continuously turning or has a preset minimum and maximum angle, the speed at which it turns, and the circuitry used to measure the change. if you want to measure speed, one solution might be best vs. detecting the initial movement of rotation on a shaft.