Torque testing is essential on torque wrenches. Torque testing is accomplished by inserting a torque transducer between the tool applying the force and the item against which the force is being 

*A torque transducer, similar to a load cell, is an electronic device used to convert torque into an electrical signal. This conversion is indirect and happens in two stages. Through a mechanical arrangement, the torque being sensed deforms a strain gauge. The strain gauge converts the deformation (strain) to electrical signals. A torque transducer usually consists of four strain gauges in a bridge configuration. 

*A key component of digital torque testers is the digital display. A digital display is used to measure the output signal from the transducer and calculates that reading into a torque value that is displayed on screen.