How does a tachometer work off the ignition coIL?

A tachometer measures engine RPM (revolutions per minute) and can work with the ignition coil by detecting the electrical pulses generated when the coil fires. Each time the ignition coil generates a spark to ignite the air-fuel mixture in a cylinder, it produces a voltage signal. The tachometer counts these signals over a specific time period and converts them into RPM readings, providing real-time information about the engine's speed. This method is commonly used in gasoline engines where the ignition coil fires with each engine cycle.