To gauge rotation of shaft 4.5 in. dia or smaller, simply clamp RIM Tach Model HS85 around shaft OD and install antirotation bracket. Tachometer outputs pulse codes of A and B, plus optional index pulse with complements. Because signal won't drift, unit requires no fault checking. Device interfaces with ac/dc drives and accommodates motors unable to maintain tight tolerances. It mounts to standard and fan-equipped motor.