Page 1 : Diagram:, , A and B — Studs, P —Pitch Scale, H —Head Scale, S —Screw Head, O — Object, , , , Zero Error (ZE):, , HS If the head scale zero coincides with the reference line of the, — pitch scale, then there is no error in the instrument and hence, , ZE = 0. |, , , , , , If the head scale zero is above the reference line of the pitch, scale, then zero error is negative. ZE = -(S x LC), , , , , , , , , , , , 48 : : :, ee Ifthe head scale zero is below the reference line of the pitch, Eo scale, then zero error is positive. ZE = +(5 x LC), Observation:, Pitch Distance moved on the pitch scale, - = eee, Number of complete rotations given to the screw head, Pitch = ———— = oe eee beeen nea nes mm, , Total number of divisions on the head scale =, , Pitch, Lest ht —, Total number of head scale divisions, LC = i a ee mm, es pe ea mm, , LL ____——, KSPUPTF, , 16, , Experiment No. 2 Dates oc. aii re, SCREW GAUGE, , Aim: i) To measure diameter of a given wire., ii) To measure thickness of a given sheet., iii) To determine volume of an irregular lamina using screw gauge., , Apparatus: Wire, ‘metallic sheet, irregular lamina, millimetre graph paper, pencil, and screw gauge., , Principle: The linear distance moved by the screw is directly proportional to the, . amount of rotation given to the screw head., i) To measure diameter of a given wire:, , Formula: | Distance moved on the pitch scale, , PyeeRiteh =, , on, Number of complete rotations given to the screw head, , Pitch, Total number of head scale divisions, , 3) Total Reading, TR= PSR+ (HSR x LC), Where PSR - Pitch scale reading, HSR - Head scale reading, , 2) Least Count, LC =, , Procedure:, 1) A known number of rotations given to the screw head, distance moved on the, pitch scale is noted and pitch is calculated. :, 2) The total number of divisions on the head scale is noted., 3) Least count is found. |, 4) When the studs A and B are in contact firmly, the position of the zero of the, head scale is observed. The number n of head scale divisions which are below, or above the reference line of the pitch scale is counted. Then zero error, :, a N= FRx 7, 5) The given wire is firmly held between the two studs by rotating the screw <, , , , , , , ~ KSPUPTE