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What Is a Torque Sensor?

Andrew Kirmayer
Andrew Kirmayer

A torque sensor measures the amount of rotational force in mechanical components. The measurements are transmitted to operators or control systems in order for machinery to function properly and engines to work correctly. In the sensor, a metal spring is attached to a strain gauge, which is affected by the torque the sensor is exposed to. Voltage is then generated based on how much torque there is. A torque transducer is usually classified as either a rotary or reaction sensor and its function is dependent on how much torque it can handle, what kind of load and drives it is built for, and the load it can tolerate when a machine or engine is started.

The reaction type of torque sensor is stationary and requires a way to attach electronics and electrical connections to the moving components being measured. More stable systems have a rotary torque sensor, in which the sensor electronics rotate with the sensor. Attaching a cable to a rotating sensor is difficult, so engineers have added digital electronics that can turn, attached slip rings, or have included radio transmitters. Strain gauge amplifiers and signal converters have also been integrated into rotating components and more complex designs even have analog to digital as well as digital to analog converters.

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Measurement errors caused by the force of mechanical components affect the accuracy of a torque sensor attached in-line. A sensor that rotates while measuring can be a solution to this problem. To prevent the sensor from being damaged, the maximum torque the sensor can frequently handle must be known. The type of load put on the sensor can vary greatly depending on where it is used. Load forces of fan or blower, conveyor or crane, to crushing equipment and crankshafts of automobile engines are rated in a scale to categorize each torque sensor.

The type of engine the sensor can handle depends on whether it is rated for a four, six, or eight-cylinder engine or a gas or diesel system. A torque sensor can handle a certain drive force created by the particular engine type. In a pump, a torquemeter can detect changes in flow, while it can measure the amount of force a stamping machine has when putting a cap on a bottle. A torque sensor can also be attached to a conveyor motor to help control tension. It is also used in electronic screwdrivers as well as in exercise and testing machines.

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Discussion Comments


@allenJo - That’s the first time that I’ve heard of that. It sounds like a neat idea, a perfect technology for the mountain biker.

The only experience I’ve had with a torque sensor (that I know of) is my electric screwdriver. It always ensures that the correct amount of torque is applied to the screw.

Sometimes some screws are more difficult to turn than others and so the sensor has to compensate. Before the electric screwdriver I had screwdriver drill bits for my cordless drill, but I find that the electric screwdriver is much more efficient in my opinion.


Torque sensors are really useful for electric bicycles. These are bicycles that have an electric motor attached to them to give them additional momentum for rough terrain or steep rides.

You use it like a regular bike but the electric motor is there for extra kick when you need it; it’s not a motorbike, it’s an actual bicycle.

Well the torque sensor will measure the amount of force on the bike as it spins and give you the amount of force that you need to keep the bike going up the hill. Think of it as similar to the cruise control that you have in your car.

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