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Tuesday, 20 May 2014

Mechanical Comparator

Mechanical Comparator Points : Mechanical Comparator, Definition, Working In this instrument the motions of measuring tip attach at ending of spindle is transmitting to pointer during a mechanism. Upper end of spindle allow beside a rocking prism. It is a frame part have two V-slots equalize to every other by distance a. End of spindle rests beside the first V-slot with its movement is transmit to this frame during a prism. Knife frame which is fixed relative to body of instrument enters the upper V-slot. Apex of upper knife-edge is centre for all affecting parts of comparator. Distance a among the V-slots form the shorter lever arm of the system, whereas, the longer lever arm is distance L as of centre of revolving of system to other end of hand, which move beside the comparator scale. Therefore magnification of instrument is L/a and is of order of 1000. Contact pressure is of order of 300 to 400 grammes with is give by a spring. Use of knife edge pivots in comparator motion excludes the influence of feasible clearance in pivots on precision of this instrument.

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