RPM: When there is a need to monitor the RPM of a rotating object, such as a wheel or shaft, there are various methods of accomplishing the task. Reed switch sensors use an internal, fast acting reed relay to indicate the passing of a rotating magnet. Zero Crossing sensors are available that are designed specifically for use with MSD-style crank trigger wheels and magnets to indicate TDC when monitoring ignition timing. A non-powered Zero Crossing sensor is also available for use in monitoring the clutch, driveshaft, or front wheel on V-Net applications. Hall Effect sensors, which require 12 volt power, are available for front wheel and ring gear applications. For applications where sensors monitor magnets on a rotating shaft, Racepak also has available split collar kits with embedded magnets.