The crankshaft position sensor is designed to record the rate at which the crankshaft is spinning. This sensor consists of a toothed metal disk mounted on the crankshaft and a stationary detector that covers a magnetic coil that the current passes through. As the metal teeth move past the coil, its magnetic field is disturbed. This causes a stream of pulses in the current. The computer can calculate the crankshaft's speed from the frequency of the pulses.