A torque sensor, torque transducer or torque meter is a device for measuring and recording the torque on a rotating system, such as an engine, crankshaft, gearbox, transmission, rotor, a bicycle crank or rotary torque sensor. Static torque is comparatively very easy to measure. Dynamic torque, on the contrary, is difficult to measure, as it generally requires transfer of some effect (electric, hydraulic or magnetic) from the shaft being measured to a static system.
One method to achieve this is to condition the shaft or a member connected to the shaft with a number of permanent magnetic domains. The magnetic characteristics of these domains will be different according to the applied torque, and therefore 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 placed on a rotating shaft or axle. With this method, a means to power the strain gauge bridge is essential, in addition to a methods to have 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 as well as an A/D converter to the rotating shaft. Stator electronics then look at the digital signals and convert those signals to some high-level analog output signal, such as /-10VDC.
A more recent development is the usage of SAW devices attached to the shaft and remotely interrogated. The force on these tiny devices because the shaft flexes could be read remotely and output without the need for attached electronics on the shaft. The probable first use in volume are usually in the automotive field as, of May 2009, Schott announced it has a SAW sensor package viable for in vehicle uses.
A different way to triaxial load cell is through twist angle measurement or phase shift measurement, whereby the angle of twist caused by applied torque is measured by making use of two angular position sensors and measuring the phase angle between the two. This technique is utilized inside the Allison T56 turboprop engine.
Finally, (as described within the abstract for US Patent 5257535), when the mechanical system involves the right angle gearbox, then the axial reaction force felt by the inputting shaft/pinion may be associated with the torque experienced by the output shaft(s). The axial input stress must first be calibrated against the output torque. The input stress may be nanzqz measured via 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 like a mechanical fuse and is an important component to have accurate measurements. However, improper setting up the torque sensor can damage the device permanently, costing time and money. Hence, the torque sensor needs to be properly installed to ensure better performance and longevity.
The performance and longevity from the miniature load cell along with its reading accuracy will likely be impacted by the design of the driveline. The shaft becomes unstable on the critical speed of the driveline and causes torsional vibration, which can damage the torque sensor. It is essential to direct the strain with an exact point for accurate torque measurement. This point is typically the weakest reason for the sensor structure. Hence, the torque sensor is purposely created to be among the weaker aspects of the driveline.