The degree of rotation can be read out from two protractors, elastic and plastic range
protractors. First, an elastic range protractor scale is fitted on the input handwheel connected to the
input shaft of the gear box. This protractor scale provides an accurate reading of 0.1o and thus one
revolution represents 6o. A resettable revolution counter is fitted to the gearbox to record the overall
input revolutions. When the twisting moment is large, the second protractor scale is required for the
readouts in the plastic range of deformation. The second protractor is fitted onto the output shaft and
provides a reading of 1o with one revolution representing 360o.