Page 55 - CITS - Electrician - Trade Practical

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ELECTRICIAN - CITS

MODULE 4: Electrical Wiring Practice, Earthing

EXERCISE 20 : To measure the diameter of conductor by

using wire gauge and micro meter

Objectives

At the end of this exercise you shall be able to
• check the scale of standard wire gauge and micro meter
• identify the parts of micro meter, check zero error and least count
• set the job in micro meter and measure the dimension of job
• measure the gauge of different wires & conductors using wire gauge.

Requirements

Tools/Equipments • Standard wire gauge (0-38 SWG) - 1 No.
• Combination Plier (165mm, insulated) - 1 No. • Micro meter stand - 1 No.
• Connector screw driver Materials
(150mm, insulated stem) - 1 No.
• Electrician knife (Insulated) - 1 No. • Different PVC copper wire
• Steel rule (30cm) - 1 No. (Any size) - As reqd.
• Micro meter (0-25 mm) - 1 No. • Bare copper & GI wire (Any size) - As reqd.
• Emery paper - 1 sheet.
• Cotton waste - As reqd.

Procedure

TASK 1 : Check the parts & xero error of micrometer
1 Draw the neat sketch of standard wire gauge and micro meter.

2 Check the scale of wire gauge and micro meter.
3 Check & identify the parts of micro meter viz- U frame, moving spindle, main scale, sub scale.
4 Move the spindle towards the face of anvil by turning ratchet to check the zero error of micrometer.
5 Zero error:
> When zero mark of main scale is coinciding with zero mark of circular scale, the micro meter has No zero
error.
> If the zero mark of circular scale is behind of main scale zero mark, the micro meter has positive zero error.
> If the zero mark of circular scale is ahead of main scale zero mark, the micro meter has negative zero error.

6 Calculate the least count of micro meter
pitch of micro meter
Least count (LC) =
No. of divisions on circular scale

Diameter = main scale reading + sub scale reading + rotating scale reading X least count ± zero error

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