When strain gauges are bonded to the shaft, the shaft becomes the transducer. The general guideline for strain gauging a shaft is that the applied torque must induce at least 150 to 175 micro-strain.

The shaft must also be calibrated, a process that usually involves loading the shaft statically and tabulating the results. Calibrating a shaft is easy to do in small systems, but as loads and shaft size increase, it becomes an onerous task.

Other concerns associated with strain gauging a shaft involve selecting a location for the strain gauge, mounting it onto the shaft and protecting it from damage through the application itself.

Any of these tasks can create problems for users who are inexperienced in such techniques. Therefore, outside contractors are usually available through the torque sensor suppliers for most applications and locations.

See also: What are the major differences between the various forms of torque measurement?