Analogue Instruments: Tachometer

The tachometer is an electrically driven, analogue instrument for displaying the vehicle engine speed. The pointer needle is oil damped to prevent impacts on the vehicle wheels, causing deflection of the pointer needle.

The tachometer is driven by an engine speed signal transmitted on the CAN from the ECM. The signal is in the form of a square wave signal of variable frequency derived from the crankshaft position sensor. The signal is received by one of the microprocessors which processes the signal. The output signal from the microprocessor is then used to drive the tachometer.

Two versions of the tachometer are used for petrol and diesel engine variants. The petrol engine variants use a display which has a maximum engine speed reading of 7000 rev/min. The diesel engine variants use a display which has a maximum engine speed reading of 6000 rev/min.