These sensors measure torque by either sensing the shaft deflection caused by a twisting force or by sensing the effects that the deflection causes.
Torque sensors are also known as torque transducers and sometimes as torque meters as well. Like load cells, torque sensors sometimes use strain gauges as their sensors, although this requires them to have a power outlet for the strain gauges as well as a program hooked up to interpret the electrical signals the strain gauges put out. Since this can be complicated, there are other methods as well, listed in the paragraph below. Piezoelectric sensors and magnetoelastic sensors can also be utilized as the central piece for torque sensors.
Torque sensors are used to determine the amount of power in an engine, motor, turbine and crankshaft within the automotive, aerospace, marine, industrial machinery, and engineering industries. Cars, trucks, motorcycles, and bicycles all measure torque using these sensors. They also act as quality control for factory machinery and measure the metal removal rates, the calibration of torque, peel forces, and friction.
There are two main types of torque sensors used today.
Reaction sensors measure both static and dynamic torque by using a stationary or non-rotating transducer. Static torque is simple and easy to measure because it requires no angular acceleration, but dynamic is more difficult because it requires electric or magnetic transfer from the shaft to a static system and involves acceleration. An example of static torque would be the torque a car produces while driving down a highway at a constant speed. Because there is no acceleration, it is not considered dynamic.
Rotary sensors use moving transducers to measure torque. They are mounted on the actual shaft, but because of this may cause space concerns. That is why they need to be well designed, so that they do not impede the production of the engine.
Common outputs for torque sensors include analog or modulated frequency, switch or alarm, analog voltage, serial, analog current, and parallel.