Size of Car Tachometers

Car tachometer sizes are often determined by their dial dimensions. Many dials have a diameter of 2 5/8 inches. Other models have diameters of 3 4/8 inches.


This is an instrument used to measure the speed of a substance or an object. The word is taken from the Greek term tachos (“speed”) and metron (“measure”).

The unit is set down as a dial with a needle. This needle is indicative of the present reading. It also shows the safe and potentially dangerous levels. The digital versions can produce numeric outputs.


These devices perform the same basic tasks; the difference is in the extra features. Some units have red line pointers that can be adjusted. Some units can function with 4, 6 or 8 cylinders. Many of these devices also have mounting hardware built in. Modern units are also compatible with many kinds of ignition systems.

Not only are the car tachometer sizes diverse, but so are the ways rotational speed is measured. Many units use LED based red beams to get the rotational speed. Other features found in these devices are minimum and maximum readings, and auto zero adjustment.

Standard Design and Form

The most basic unit will measure the speed at which a mechanical apparatus rotates. This is the type you see in car dashboards. What the device does is determine the engine drive shaft RPMs (revolutions per minute). This is important because running engines high can shorten its lifespan.

The traditional tachometer may consist of a generator connected to the engine drive shaft. In this case, the measurements of the RPM are scaled to the electric current.

In other cases, the device just determines the rate which the ignition relays the engine sparks. Older systems require physical contact with the gadget being measured.

That is no longer necessary with devices that use lasers. What these devices do is pulse a light beam on the object. These laser devices can be affixed to the system or be portable.

Other Information

Some doctors use the tachometer in medicine. It can be used to monitor blood flow rate. This is made possible by placing a small device in the artery.

There are many car tachometer sizes to choose from. While there are still traditional devices sold, those that use laser are more ideal. They are accurate and easy to carry around. You can find many of these online. These are also available in car accessory shops.

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