Tachometer: How does this device work?

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A tachometer is a device used in a car to measure engine revolutions or engine crankshaft revolutions.

Thus, the tachometer pointer indicates the number of crankshaft revolutions per minute on an analog or digital display.


The history of the tachometer in a nutshell

The first tachometer was built in 1817 by the German engineer Deidrich Uhlhorn. At first, the tachometer was only used to measure the speed of locomotives, but over time it also found its way into cars.

The first tachometers were mechanical and were based on the measurement of centrifugal force.

How does a modern tachometer work?

In modern cars, the tachometers are electronic. The engine control unit obtains Data on crankshaft revolutions, which cooperates with the crankshaft revolution sensor.

It should be added that if the crankshaft speed sensor stops working, the engine will shut down, and if it does not work before the engine starts, the engine will not start.

As mentioned above, the tachometer in a car shows the number of revolutions of the crankshaft in a certain time, in this case, per minute.

The tachometer almost always has a marked red field, which alerts the driver to the area of ​​dangerous revolutions. The driver, therefore, always has an overview of the current speed and can thus reduce the engine speed by taking off the gas and returning the engine to a safe speed.

Can high (red range) revolutions damage the engine?


Keeping the engine at high speeds in the tachometer's red zone for a long time harms the engine because, at that moment, the engine is not sufficiently lubricated with engine oil.

This causes individual components to overheat, which can ultimately cause a seized engine. However, keeping the engine in the red speed range for a long time may not immediately lead to a malfunction, but at least it may cause increased wear of some engine parts.

Difference between mechanical and electronic tachometers: