A torque sensor measures and monitors the torque applied in a rotating system. They are often used in engine, crankshaft, gearbox, transmission, & rotor. The torque required to break down a rotating shaft is called static torque. Whereas, the torque required to rotate the shaft of a motor is called dynamic torque. It is easy to measure static torque. A dynamic torque measuring device has to take some other effects (hydraulic, electric, or magnetic) into consideration as well.
How do they work?
There are different ways to measure the torque of a rotating system. A series of permanent magnetic domains are attached to the rotating body. The magnetic characteristics of these magnets will change with respect to the torque. They are used for in-vehicle applications.
Otherwise, a strain gauge is used to measure the torque. Modern torque sensors are equipped with a strain gauge. They have a stretchable medium which has a conductive film coating. Under stress, this medium stretches, and the film along with it. Thus, the change in torque increases or decreases the conductance of the film. This conductance change is measured and converted into torque equivalents.
The strain sensitive patterns are very thin zig-zag lines above the surface of the sensor. They are less sensitive in the direction perpendicular to the axis, whereas most sensitive in the direction of conducting lines. So, when the gauge is stretched in one direction, the resistance of the element increases.
Strain Gauge in a Torque Sensor
Torque is the force applied to turn an object. While applying torque force at the shaft, a slight deformity is induced. An attached strain gauge in the shaft senses the same deformity. The strain gauge included in the sensor measures the deformity and outputs the value as torque equivalents.
Torque sensors are very reliable, stable, robust, & cost-effective. They were found a long ago, and the design quality has improved over the years. Advanced digital processes have improved manufacturing methods. Hence, modern torque sensors are light and very compact. Torque sensors are deployed in a wide range of applications. They are used anywhere a rotor or motor is used. Industries use torque sensors to monitor the production machinery as well. They are also used in offshore, aerospace, and laboratories as well.