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Topic: rotary torque sensor (Read 72 times) previous topic - next topic



I want to measure torque on rotating shaft. After hours of searching i could not find any option which doesnt cost a fortune. Existing sensors with data loggers, as a complete solution, are expensive.

My calculations shows following measurements:

max. torque: 75 Nm
max. rotary speed: 100 rpm
max. power: 300

i want to build my own system for these requirements and i want to use arduino as a data logger. But the problem is, i have no idea about what i should be doing. Here are my questions:

1-The output voltage is linear to torque input. And the output voltage of sensor is +/- 5 V DC. But how am i going to know, which torque value gives which output voltage?

2-Sensor has inner resistance and some other specifications. How do they affect my end results?

3-Did you have any other idea instead of using a rotary shaft to shaft torque sensor?

Thanks a lot, every feedback and every idea means so much to me!


I've considered such a problem recently, but have not researched.  One of my college classmates used this problem for his senior design project, but that was 15 years ago.  He had the same problem, the only commercially available solution was very expensive.  I don't remember what he used in his final solution.

My thoughts: Use a strain gauge on the shaft.  Circuit to measure the strain gauge is also on the shaft--both rotate with the shaft.  Power the circuit using a wireless charger.  Communicate the measurement with a bluetooth module or some other wireless device.  All of this should be sufficiently small so it does not create a balancing problem and to prevent damage to the torque measurement hardware.

This is all hypothesis and I have done absolutely NO testing or prototyping of any kind.

Maybe this will help jumpstart some ideas for you.


If this is anywhere near correct: http://planetcalc.com/1908/#, you are way off on the power value.

My solution would be to couple a DC electric motor to the shaft. Apply power to the DC motor to rotate in the opposite direction to your shaft. Adjust the current to the electric motor until it is able to slow your test shaft. Measure the motor's current and voltage at that point and then compute the power and then the torque needed to slow your shaft.

Heat generation will be a problem, so the test needs to be done rather quickly.



You didn't say if it was rotating or stationary torque reading?
Also, what kind of torque are you talking about?
A car engine puts out torque as does a servo.
One would use completely different methods.
If it is a static torque, you could use the part they use in a
cheap bathroom scale.
Rotating torque can be measured by having two pickups at the
ends of a shaft that has some spring. If there is torque one end
rotates such that there is an increase in phase angle between the
to pickups. Magnets and hall effects make sense here.
Calibration is easy, torque is measure as some weigh at some
distance. Put an arm on your measuring setup and hang a
weight on it.
If measuring inch-pounds, say 10 inch-pounds, use a 5 inch
arm and 2 pound weight.

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