A Torque Sensor is a sensor that converts a torsional mechanical input into an electrical output signal.
The torque sensor is used to measure the torque on a rotating system such as an engine, crankshaft, gearbox, transmission, etc. Torque can be divided into two types-Static torque and Dynamic torque.
Static torque is relatively easy to measure compared to dynamic torque. Dynamic torque is not so easy to measure since it normally requires transfer of some effect (electric or magnetic) from the shaft being measured to a static system.
Torque can be measured by rotating strain gauges as well as by stationary proximity sensors.
Rotary sensors must be mounted on the shaft. An integral slip ring assembly is used to transfer the electrical signal from rotating electronics to stationary electronics. The slip ring consists of brushes which rub on rotating ring, providing an electrical path for the incoming excitation and the outgoing signal voltage. At low to moderate speeds the electrical connection between the rings and brushes are relatively noise free, but at higher speeds noise will severely degrade their performance.
Typical max speeds will be in the 5000 rpm range for a medium capacity torque sensor. Finally, the brush ring interface is a source of drag torque that can be a problem especially for very low capacity measurements where the driving torque will have trouble overcoming the brush drag.
Proximity and displacement sensors can also detect torque by measuring the angular displacement between shaft's two ends. By fixing two identical toothed wheels to the shaft at some distance apart the angular displacement caused by the torque can be measured. Proximity sensors or photocells located at each toothed wheel produce output voltages whose phase difference increases as the torque twists the shaft.
Applications of Torque sensor
- Determining the power of engine or motor
- Clutch testing
- Motor/Pump testing
- Automotive brake testing
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