What is a Revolution Counter?

Mary McMahon

A revolution counter is a device that tracks revolutions of a disc, shaft, or similar object. It can return data about the speed of rotation, as well as simply recording the number of rotations. Some are analog, requiring a mechanical connection with the device they measure, while others may use techniques like laser sighting to collect information. A well-known example of a revolution counter is the tachometer in a car, with a display providing information about the engine's number of revolutions per minute.

An odometer is a type of revolution counter.
An odometer is a type of revolution counter.

The revolution counter can return data in the form of revolutions per minute, often with a needle sliding along a graduated scale. The scale may have shaded zones indicating safe operating speeds. High speeds may endanger the equipment and the scale could include green, yellow, and red zones so an operator knows how well the system is functioning. If the revolution counter starts to enter the red zone, the operator can make adjustments to slow down the revolutions per minute to reduce the risks of damage or injury.

It can also operate with a simple rolling ticker, clicking over a new number with each revolution. The counter can display digitally or mechanically. This displays the total number of revolutions, but does not provide a time frame. In the case of a device like an odometer in a car, a revolution counter tracking rotational speed moves a counter reflecting distance traveled. The revolution counter will turn more slowly at lower speeds, and will speed up at higher ones, tracking overall distance.

The sensitivity of a revolution counter can vary. Some are capable of very detailed measurements, including fractions of a revolution, while others are simpler. Generally, the more complex, the more expensive. More complex devices are also more fragile. Their sensitivity may be ruined if they are handled incorrectly or not maintained properly. Housing the device in a protective casing can help keep it reliable and functional. Periodic calibration may be important to make sure the measurements stay accurate.

Scientific suppliers, as well as companies selling machine parts, usually sell revolution counters. It is possible to special order certain products for particular applications, or to buy generic models designed for a wide range of uses. Most devices come with a guarantee, and should not fail within a set time period or number of revolutions. If a device breaks or fails to register data properly, the company will send a replacement at no charge.

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Discussion Comments


In a way that was probably unintentional, these can be used to mark achievements. Ever see a family gathered around to watch an odometer reset to 0? Putting 100,000 miles on a car is considered to be a milestone.


@Terrificli -- these counters are a very early form of automation. Think about how people used to have to "count heads" to figure out how many folks were visiting a theme park or whatever else. Simple revolution counters made it easy to automate that process -- a way to let machines handle a task of drudgery to free people up for other things.


We've all seen these in use from time to time. Think about turn styles used at zoos, baseball games and all over the place to keep up with the number of people visiting.

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