The ability to measure the speed or position of a rotating shaft is necessary to the proper functioning of many types of machinery. Speed sensors, timing sensors, and encoders are used in applications as varied as automobile ignition controls, exercise equipment, and CNC machine tools. An example of a typical Hall-effect speed sensor is shown in Figure 8-1. When a toothed steel target (such as a gear) is rotated past its flat end, this device provides a train of output pulses, one for each passing target feature.
Figure 8-1 Geartooth sensor assembly. (courtesy of Cherry Electrical Products)