What is a car tachometer?

The tachometer is set on the instrument panel and placed symmetrically with the speedometer. The tachometer works according to the magnetic principle. It receives the pulse signal generated when the primary current in the ignition coil is interrupted, and converts the signal into a displayable speed value. The faster the engine speed, the more pulses generated by the ignition coil, and the greater the speed value displayed on the instrument.

Nowadays, cars are generally electronic tachometers with hands and LCD digital display. There is a digital integrated circuit in the instrument, which drives the pointer to move or display digitally after calculating the voltage pulse transmitted by the ignition coil. There is also a tachometer, which takes out the pulse signal from the generator, sends it to the tachometer circuit for interpretation, and then displays the speed value, but the value is not accurate due to factors such as generator belt slipping.

Extended data

The engine speed is related to the number of times of work done per unit time or the effective power of the engine, that is, the effective power of the engine changes with the speed. Therefore, when explaining the effective power of the engine, it is necessary to indicate its corresponding speed at the same time.

The effective power specified on the nameplate of the engine product and its corresponding rotational speed are called calibrated power and calibrated rotational speed respectively. The working condition of the engine at rated power and rated speed is called rated working condition. Rated power is not the maximum power that the engine can emit, but the maximum use limit of effective power based on the purpose of the engine.

The rated power value of the same engine is different for different purposes. Effective torque also varies with engine operating conditions. Therefore, the automobile engine takes the maximum torque it can output and its corresponding speed as the index to evaluate the engine power performance.

Baidu encyclopedia-engine speed

Baidu encyclopedia-automobile dashboard