Job Role Automotive Service Technician

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Sector: Automotive (Qualification Pack Code : ASC/Q01402)
PSS Central Institute of Vocational Education Shyamla Hills, Bhopal – 462013, Madhya Pradesh, India _________________________________________________________

UNIT 4 : Measuring Equipment's Session-1: Handling and Usage of Direct and
Indirect measuring instruments



Slide No.

Session Objective




Measuring Instruments


Reading of Vernier calliper


and measuring diameter of

the cylinder




Session Objectives
1. The student will be able to explain importance direct and indirect measuring instruments .
2. Able to identify direct and indirect measuring instruments .
3. Able to use steel rule and steel tape 4. Able to use vernier caliper, micrometer and vernier depth

A measurement is assigning a value to length, mass and time. The importance of measurements in science is the exactness. You can not verify laws, properties or science experiments without having exact measurements. If measurements are not given, and you try and recreate a project someone else did, you will not come up with the same result they did . Accurate measurement is important because it helps in quality assurance and giving of accurate calculations in almost every field. Lack of accurate measurement causes errors which may be quite costly and dangerous. Instruments used for measuring basic units such as mass, length and time or derived units such as speed, acceleration, pressure etc; are called measuring instruments or equipment.

Measuring Instruments
Important measuring instrument used in our daily life. Similarly measuring instruments are also used in automobile serviceability. Important measuring instruments used are Dial gauge, Bore Gauge, Vernier caliper, Depth Gauge, Micrometer, Hydrometer and Multi meter etc. We will try to understand the handling and usage of these measuring equipment’s. Measuring instruments used in automotive can be classified as below: 1. Linear measurement • Direct measuring instruments • Indirect / instruments for transferring measurements 2. Angular measurement 3. Plane surface measurement

Direct measuring instruments
The measuring instruments, which do not require the help of other instruments for measuring are called direct measuring instruments. Usually these instruments have a line, which is divided in equal parts, called graduated scale. commonly used direct measuring instruments are: Steel scale/rule: It is a line measuring device. It is the simplest and most common measuring instrument used in inspection. It works on the basic measuring technique of comparing an unknown length to the one previously calibrated. It consists of a strip of hardened steel having line graduations etched or engraved at interval of fraction of a standard unit of length. The scale can be either 150 mm long or 300 mm or 600 mm or 1000 mm long.

Steel tape
A measuring tape is a flexible form of ruler. It consists of a ribbon of cloth, plastic, fiber glass, or metal strip with linear-measurement markings. It is a common measuring tool. Its flexibility allows for a measure of great length to be easily carried in pocket or toolkit and permits one to measure around curves or corners. For workshop a 3m length tape can be used.

Vernier caliper
The meter scale enables us to measure the length to the nearest millimeter only. Automobile technicians need to measure much smaller distances accurately. For this a special type of scale called Vernier scale is used. The Vernier Caliper is a precision instrument that can be used to measure internal and external distances extremely accurately. The vernier caliper is usually a manual caliper. Measurements are interpreted from the scale by the user

Parts of a Vernier calliper Outside jaws: used for measuring external diameter or width of an object Inside jaws: used to measure internal diameter of an object Depth probe: used to measure depths of an object or a hole Main scale: scale marked every mm Main scale: scale marked in inches and fractions Vernier scale gives interpolated measurements to 0.1 mm or better Vernier scale gives interpolated measurements in fractions of an inch Retainer: used to block movable part to allow the easy transferring of a measurement

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Job Role Automotive Service Technician