Tachometer

Tachometer comes from two Greek words: tachos meaning speed, and metron, meaning measure. 

In the case of an analogue dial, the tachometer shows the measuring unit in RPM or revolutions per minute. However, in recent times digital tachometers are prevalent. The description of the first tachometer ever was given by Bryan Donkin in 1810 to the Royal Society of Arts. Because of this, he was facilitated with a Gold medal by society. 

The first-ever tachometer was used to measure a vehicle’s speed or an engine in 1840. However, Karl Benz developed the first petrol aided automobile in 1886. The first automobile featuring a Tachometer is still unknown.

Types of a Tachometer

There are mainly four types of a tachometer:

1.   Analogue Tachometer

An analogue tachometer consists of a dial and needle-type interface. They cannot store readings and calculate details like deviation and average. In this type of tachometer, speed is convertible to voltage with the help of an external frequency. This voltage is showcased with the help of an analogue voltmeter.

2.   Digital Tachometer

A digital tachometer consists of a LED or an LCD output signal and a storage memory. They can perform statistical operations and precisely measure and monitor any time-based related quantities. Digital tachometers are most common and give digital numerical readings instead of needles and dials.

3.   Non-Contact and Contact Tachometer

The Non-contact and contact tachometer work on methods of data acquisition. The contact tachometer is attached to the rotating shaft. A magnetic sensor or an optical encoder is used in this type. In contrast, the non-contact tachometer is best suited for mobile applications that use either a laser or an optical disk.

4.   Time and Frequency Tachometer

Time and frequency tachometer work on the measurement methods. The time measuring device calculates speed by calculating the time interval gap between the incoming pulses. They are ideally suited for low-speed measurements. On the other hand, the frequency measurement device measures speed by calculating the incoming pulses’ frequency and is best fitted for high-speed measurements.

Uses of a tachometer

After finding the types and tachometer meaning, let’s look at the various kinds of applications or uses of tachometer. Some of them are:

1.   Tachometers in the automobile services

A tachometer is widely used in revolution counters in aircraft, cars, and other automobiles to portray the rotating rate of the engine’s cylinder head and have labels indicating a secure range of rotating speeds. 

This is used to help the driver choose adequate gas-pedal and gear settings for different driving situations. In the case of analogue tachometers, speeds above the maximum safe speed operating are labelled by an area marked in red, signalling the expression to revive the engine’s maximum safe limit.

2.   Tachometer in traffic engineering

A tachometer is used to estimate traffic volume/flow and speed. A vehicle consists of a sensor and produces “tach runs,” which in return record the data of traffic. 

In order to get significant results which are statistically correct, we need a high demand of runs, and thus bias is calculated by the day of the week, season and time of the day.

3. Tachometers in trains and light rail automobiles

A tachometer is highly used in devices to sense speed. They are also referred to as WIG “wheel impulse generators.” Tachometers are used in rail vehicles extensively. One of the most common types is “Hall effect sensors” and “optoisolator slotted disk sensors.“

4. Tachometer in an audio recording (analogue)

A tachometer is a device used to measure the speed of an audiotape in analogue audio recording. A tachometer is used for sound playback in high fidelity. However, it is not applicable for synchronised recording with the help of a movie camera. To resolve these purposes, peculiar recorders with record pilot tones are used.

Conclusion

A tachometer is a device used to indicate the rotary/angular speed of a rotating disk/shaft. However, the term tachometer is restrained to electrical or mechanical instruments which involve immediate speed values in RPM ( revolutions per minute). 

A Tachometer has a variety of purposes to solve in the automotive world, including cars, tractors, trucks, vehicles, trains, and even aircraft. Along with traffic engineering, a tachometer is also used in audio (analogue) recordings. A stroboscope is an instrument that can be used as a tachometer by illuminating objects in a rotation so that they appear to be stopped from moving.