A torque sensor, torque transducer or torque meter is a device for measuring and recording the torque on a rotating system, including an engine, crankshaft, gearbox, transmission, rotor, a bicycle crank or Compression Load Cell. Static torque is fairly simple to measure. Dynamic torque, however, is not easy to measure, as it generally requires transfer of some effect (electric, hydraulic or magnetic) from the shaft being measured to a static system.
One way to do this is always to condition the shaft or even a member attached to the shaft with several permanent magnetic domains. The magnetic characteristics of these domains will vary in accordance with the applied torque, and so can be measured using non-contact sensors. Such magnetoelastic torque sensors are typically used for in-vehicle applications on racecars, automobiles, aircraft, and hovercraft.
Commonly, torque sensors or torque transducers use strain gauges put on a rotating shaft or axle. With this method, a way to power the strain gauge bridge is essential, in addition to a means to get the signal from the rotating shaft. This is often accomplished using slip rings, wireless telemetry, or rotary transformers. Newer kinds of torque transducers add conditioning electronics plus an A/D converter for the rotating shaft. Stator electronics then read the digital signals and convert those signals to some high-level analog output signal, like /-10VDC.
A much more recent development is the use of SAW devices connected to the shaft and remotely interrogated. The force on these tiny devices as the shaft flexes could be read remotely and output without resorting to attached electronics on the shaft. The probable first use in volume will be in the automotive field as, of May 2009, Schott announced it features a SAW sensor package viable for in vehicle uses.
Another way to measure Rotary Torque Sensor is by way of twist angle measurement or phase shift measurement, whereby the angle of twist as a result of applied torque is measured by using two angular position sensors and measuring the phase angle between them. This method is utilized in the Allison T56 turboprop engine.
Finally, (as described within the abstract for US Patent 5257535), in the event the mechanical system involves a right angle gearbox, then this axial reaction force experienced by the inputting shaft/pinion may be related to the torque gone through by the output shaft(s). The axial input stress must first be calibrated from the output torque. The input stress can easily be measured wbtbtc strain gauge measurement from the input pinion bearing housing. The output torque is easily measured using a static torque meter.
The torque sensor can function such as a mechanical fuse and it is an important component to have accurate measurements. However, improper installing of the torque sensor can damage the device permanently, costing money and time. Hence, the torque sensor needs to be properly installed to make certain better performance and longevity.
The performance and longevity from the Multi Axis Force Sensor as well as its reading accuracy will likely be affected by the design in the driveline. The shaft becomes unstable at the critical speed in the driveline and results in torsional vibration, which can damage the torque sensor. It is essential to direct the strain to an exact point for accurate torque measurement. This aspect is usually the weakest point of the sensor structure. Hence, the torque sensor is purposely designed to be one from the weaker components of the driveline.