Sigma comparator changes its magnification - Metrology & Quality Control

Q.  Which type of comparator changes its magnification, when distance between cross strip hinge and knife edge is varied?
- Published on 07 Aug 15

a. Johansson mickrocator
b. Solex pneumatic comparator
c. Projector comparator
d. Sigma comparator

ANSWER: Sigma comparator

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    Discussion

  • Sravanthi   -Posted on 23 Oct 15
    - Sigma comparator is a mechanical comparator and consists of knife edge, cross strip hinge, Y arm, a fixed and a movable block, etc,.

    - The screws on the plunger can vary the distance between hinge and the knife edge. Total magnification of [(l / a) x (R / r)] can be obtained by this instrument.

    - In sigma comparator, plunger is mounted on slip diaphragm to obtain frictionless movement. The moving member of cross strip hinge bears knife edge. The distance between knife edge and cross strip hinge can be varied by the screws on the plunger.

    - The first magnification stage of ( l /a) is obtained when Y arm of length l is attached to cross strip hinge.

    - Second stage magnification of (R / r) is provided when Y arm is attached to phosphor bronze strip which moves over the drum and drives the pointer to measure the readings.

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