# Chapter-3| Linear Measurement and Instruments used for Linear Measurement

Linear Measuring instruments are designed to measure the distance between two surfaces or points ( end measurements) like Vernier Caliper, Micrometer does.

Video of Linear Measurement

The Basic Fundamental unit of linear measurement in mm. It is one of the seven units

Even we can say in all places were measurement used, also used in our day-to-day life.

A scale is the best example to understand linear measurement. A scale is the first instrument of every student to measure lines, the distance between two points.

Vernier Calipers and Micrometer, we can divide into Analog and Digital. Analog is economical and simple, less accuracy than Digital. On another hand, Digital comes with more accuracy and costly.

## Instruments Used for Linear Measurement

### Vernier Caliper(Digital & Analog)

Vernier Caliper is a widely used linear measurement instrument. It is used to measure linear dimensions like length, diameter, depth.

There are three types of Vernier Caliper

1. Analog Vernier Caliper
2. Dial Vernier Caliper
3. Digital Vernier Caliper

### Analog Vernier Caliper

It is the most common Instrument of measurement, It consists of two types of scale

The main scale and the Vernier scale that can slide along the main scale.

Two types of measurement we can do, the first one is through the external jaw (measure external dimensions) and another one is internal jaw (measure internal dimensions)

The most common Least count of Analog Vernier Caliper is 0.02 mm. You may also find vernier least count of 0.05 mm or 0.1 mm

### Dial Vernier Caliper

Vernier scale is replaced by Dial indicator in dial vernier caliper. Dial indicator helpful for easy measurement understanding.

### Digital Vernier Caliper

Digital Vernier Caliper is upgrading version of Analog Vernier Caliper, which is a widely used linear measurement instrument with a least count of 0.01 mm, more accurate than Analog.

### Micrometer(Analog,Digital, Inside & Depth)

The micrometer is more precise and accurate than Vernier caliper. Usually, two types of Micrometer are

1. External Micrometer
2. Digital Micrometer

### External Micrometer

External Micrometer is also known as Outside Micrometer or External Micrometer.

It is used to check outside diameter of the shaft by the means of the accuracy of 0.01 mm or up to 0.001 mm.

### Digital Micrometer

Digital Micrometer is a very popular instrument these days because of its easy of compactness of taking an observation. Digital Micrometer can observe measurement in mm or inch depend upon our need basis.

The accuracy of Digital Micrometer 0.001 mm which is highly accurate and precise than External Micrometer. You can choose Digital Micrometer with an accuracy up to 0.001 mm if the cost does not matter

Main Differences between Vernier Caliper and Micrometer

### Scales & Measuring tape

Steel scale is single piece linear measuring instrument. Steel scale indicates two units that are cm and inches, cm division on one side and inches, on another side.

Steel scale is used to measure the simple length in one dimension. Usually, the least count of steel scale is 1 mm. Steel scale applied in easy comparison, where less precision required.

### Height Gauge(Vernier Height Gauge & Digital Height Gauge

Vernier height gauge used to measure vertical dimension from reference ground. Vernier Height Gauge consist of a graduated scale or bar is held in a vertical position by a finely ground fixed base.

### Vernier Depth Gauge

Vernier Depth Gauge as the name suggests is used to measure the depth from the surface of reference of an object. Vernier caliper also has depth bar but this can not be used as the standard measurement.