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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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