The span between the output signal values at nominal torque and at zero torque. Usually two separate sensitivities are specified for HBM torque transducers, one for clockwise torque and one for counterclockwise torque.
Fig. 1: Sensitivity and nominal torque
The sensitivity C characterizes the slope of the characteristic curve. The characteristic curve is chosen as the straight line connecting the output signal SM0 determined with mounted but unloaded torque transducer (initial torque signal) and the output signal Sn at nominal torque determined at increasing torque. This gives the simple equation
C = Sn − SM0
The sensitivity and the nominal torque form a known pair of values combining a given torque and the respective span of the output signal. If two such pairs of values are given they can be used for setting the amplifier. Usually, the second pair of values is zero torque and zero output signal span (i.e. output signal = initial torque signal).
The nominal value characterizing the transducer’s sensitivity. Usually it is equal for clockwise and counterclockwise torque.
The nominal sensitivity is a value characterizing the respective transducer’s type and measuring range. However, the actual sensitivity of the individual is equal to the nominal sensitivity only within specified tolerances.
The permissible deviation of the actual sensitivity from the nominal sensitivity. It is given as a percentage with respect to the nominal sensitivity.
For HBM torque transducers the actual sensitivity of the individual is determined before delivery. The value is documented in the test certificate or calibration certificate. For this reason the sensitivity tolerance is not taken into consideration when determining the accuracy class.