# twist sensitive resistor?

Discussion in 'Electronic Basics' started by Dave, Jul 13, 2005.

1. ### DaveGuest

I have science project that involves measuring a small torque, or
twisting force.

Is there a torque sensitive resistor I can buy? Or perhaps a torque
sensitive capacitor? I can integrate it into an existing circuit if I
can find one.

Thanks, Dave

2. ### Henry KolesnikGuest

You could make a capacitor to be torque sensitive. Attach one plate to the
shaft and the other to a fixed point. The capacity will vary with the
torque.

HTH

5. ### JeffMGuest

Henry Kolesnik top-posted:
That will measure angular displacement
(which may be an analog to torque),
but it doesn't measure force or radius.
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6. ### JeffMGuest

Is there a torque sensitive resistor I can buy?
Next time you post to multiple groups
post just ONCE
and put ALL the groups in which you want the question to appear
on the Groups line.

This allows EVERYONE who reads the question
to easily see ALL the solutions that are proposed.
..
..
..
Henry has already suggested a variable capacitor.
That can be an analog of torque
(as can a potentiometer--which is smaller and cheaper).
Both of these will likely require gearing
to get any kind of resolution
(leaving you with forward/backward lash).
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..
A strain gauge measures force (which can also be an analog of torque).

7. ### Jonathan KirwanGuest

How small is the torque? The magnitude such as between two small,
balanced and suspended masses and another pair of masses as in the
Cavendish experiment?
What is twisting? If it is the famous dumbbell experiment, for
example, you can just use a simple small-milliwatt 635nm diode laser
or better yet a HeNe laser and bounce it off of a tiny bit of mirror
attached to one of the suspended masses. You can easily align the
beam so that it reflects and then hits an exact point on a distant
ruler and when the suspended mass shifts slightly through some angle
X, the reflected beam will go though a deflection change of 2X. This
may be just fine if you are replicating Cavendish for a science
project.

Jon

8. ### JamieGuest

One of our machines at work has an optical pick up on on
each end of a drive shaft. when the machine is at idle (no torque)
the 2 opticals are perfectly aligned or near it. as the shaft starts
to twist under load, the drive side will get ahead of the output
side of the shaft thus causing the two opticals to miss align and
produce an offset of pulses ect./

also you could simply measure the load current on the drive device?
there are also things like load cells that use a capactive method.