Engineering in Kenya

Mechanical Tachometer

Posted by on May 11, 2018 in Mechanical Engineering | 0 comments


A mechanical tachometer in the most simplest and basic form, it is an instrument used to measure rotating speed of any given mechanical device.  To give a familiar example is the tachometer fixed in automobile dashboards.

Mechanical Tachometer Mechanical TachometerMechanical Tachometer Introduction

As explained above in a simple approach mechanical tachometer is not complex or complicated. It is basically an instrument which is used for measuring the revolution speed of any rotating object, for instance a shaft or motor.

A mechanical tachometer has its specific utilization in various fields and it has it uses in the marine engineering field as well. In this particular field, it is used to gauge the speed of marine diesel engines on the board ships and whether they are rotating in either the ahead or stern direction. Get to know the types of tachometer apart from mechanical tachometer and the working principle of the tachometer in this article.

The speed of a rotating shaft or motor needs to be measure as this has some several uses. For instance on a ship a navigating officer at the bridge or an engineer in the ECR needs to know in which speed and direction the engine is rotating.

Other Types of Tachometer Alongside the Mechanical Tachometer

Tachometers may actually seem similar while taking a glance from outside. This is because the tachometers including the mechanical tachometer have a display that shows the speed. However, they are based on different principles and there are various given types of tachometers which include the following: Magnetic Tachometers, A.C. Tachometers, D.C Tachometers as well as Mechanical tachometers among others.

468x60 animated Mechanical Tachometer

Though there is a difference in the tachometers, there is a basic purpose among all the tachometers which is the same irrespective of the construction of a particular tachometer such as the mechanical tachometer. Bellow is some interesting facts about some tachometer namely the Mechanical tachometer and the D.C tachometer.

468x60 animated Mechanical Tachometer

Mechanical tachometer: as it can be seen from the inside, mechanical tachometer is a type of tachometer that is nothing but a linkage of the shafts, rotational weights and gears. When the input shaft which is seen at the horizontal of the tachometer rotates the vertical shaft it as well rotates the weight that is attached to it which are the hinged and are also free to move inwards and also outwards.

Then the movement of these flyweights rotates a given pointer which is calibrated to show the speeding in the desired set units such as RPM.

D.C Tachometer: the D.C tachometer can be compared to an Ammeter. The Ammeter can be used in measuring the current such that the pointer in this particular case is deflected in proportion to the current that flows through a given moving coil which gets the current from the D.C generator.

This can be seen in the inside of the D.C tachometer and the permanent magnets instituted inside provide the necessary magnetic flux for the operation whereas the spinning motion is given by the input from the shaft or the motor whose speed has to be measured.

Other than telling the magnitude this arrangement has as well the merit of telling the direction of rotation of the shaft that is in the ahead astern or the direction.

Mechanical Tachometer Uses and Various Styles

The speed of the engine of an automobile is turning and is measured in revolutions per minute abbreviated as (RPM) by a tachometer.  Most motor vehicles have got the standard shift transmission and given that it is necessary to shift at the best and possible RPM in order to get a better acceleration and also to cut short on the gas expense, then the indicator in the mechanical tachometer is very useful.

In a case where a car is fitted with an automatic transmission then the tachometer is not utilized often. Mechanical tachometer indicator move to the red zone while the engine is running very fast, the indicator in the red zone is an alert or an alarm to the drive in order to safe guard the engine from any damage.

Majority of the tachometers display single digit indicators with a small mark that reads RPMX 1000. This explains that the reading in the tachometer should be multiplied by the 1000 in order to get the correct RPM.

The mechanical tachometer is also able to measure the rate at which the sparks to the engine is transmitted by the ignition system. The tachometers are used even in the medical science; the doctors may use these tachometers to measure the blood flow rate from the spinning speed of the turbine in the device.  The device is referred to as a harematachometer.

A physical contact between the instrument and the device that is being measured is required in the traditional tachometer. Given that it is impossible to provide the physical contact in applications where safety is more important then a laser tachometer may be used over a distance to take the measurement.

A tight beam of light from the laser tachometer is throbbed against a rotating element. In the view of the fact that the rotating element will contain a reflective spot, then the tachometer will measure the rate at which the reflection back of the light beam, which in turn will assist in calculation the speed of the given device.

Today, there are wide ranges of hand-held and also portable tachometers, which can be used to measure speeds of up to 250,000 revolutions per minute.

An infrared tachometer as the name suggests uses an infra red-beam. The red-beam which is not in any way affected by ambient light, in measure the rotating speed of drills, hones, saws, motors, fans, engines, generators, compressors.

There are two main drawbacks when it comes to mechanical tachometers. Weights have inertia and because of this they are not accurate and also secondly the mechanical tachometer doses no give an indication of both the direction and the rotation. Yet the major merit of measuring rotating speed of any mechanical device cannot be ignored when it comes to a mechanical tachometer.

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