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- Phone: 86 0512 62697848
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How to measure torque with an angle sensor?
Angle sensors to measure torque have many advantages, and with the new development of inductive angle sensors, this technology that is considered obsolete is now making a comeback. Measuring the torque applied to a fixed metal shaft is usually simple. If the elastic limit of the shaft is not exceeded, the amount of twist in the shaft is proportional to the torque. How to measure torque with an angle sensor?
A common method is to infer torque based on the power required by the rotating shaft, which usually means measuring the current provided to the motor that drives the motion. This measurement method is simple but not accurate because the current consumption depends on other factors such as speed, voltage supply, bearing condition, temperature, etc.
The precise method is to measure the distortion in the shaft using a strain gauge or surface acoustic wave device. The accuracy of this measurement method is greatly improved, but the slip ring or the complexity of some wireless signal transmission methods is required between the shaft and the external strain gauge.
When zero torque is applied, the signals from the two resolvers show zero phase shift. When torque is applied, the phase of one output appears to be relative to the other output. Therefore, the phase shift is proportional to the applied torque. With a multi-speed resolver with a large number of cycles, only a small amount of distortion is required to produce a significant phase shift. In other words, it is a highly sensitive technique suitable for measuring distortions of <1 degree or even <0.1 degree.
In practice, the shaft length required for this method can be <25mm. This can be achieved by using a deliberately flexible shaft or by concentrically arranging the resolver and using a rigid torsion spring to connect the inner and outer parts of the shaft.