Vadodara Institute Of Engineering

Name: Chaturvedi Anupam(501)Topic : Comparators

Teacher : Miss. Shalini SinghDivision : Mechanical 3

Semester : 4th

Comparator

• Introduction :• A comparator is a precision instrument

employed to compare the dimension of a given component with a working standard (usually slip gauges).

• It thus does not measure the actual dimension but indicate how much it differs from the basic dimension.

• In mass production identical component parts are produced on a very large scale.

• To produced interchangeability these parts produced very close dimensional tolerance.

• As a result, inspection is often more concerned with the dimensional variation from the standard parts.

• The micrometer and vernier calliper are not more feasible because skill involve and time required to measure the dimension.

• In such case comparator is more suitablefor the measurement.

Basic principle of operation

• The comparator first adjust on zero on its dial gauge with a gauge block in position.

• The gauge block is of dimension which the work piece should have.

• The work piece to be checked is then placed in position and comparator gives the difference in dimension in relation to the gauge block.

• Dimension may be greater, less or equal than the standard dimension.

• If the dimension greater or equal than the standard gauge its indicate on dial gauge.

• Thus comparator does not give the dimension of the work piece but just give the difference b/w work piece and standard gauge.

Mechanical optical comparator

Sigma comparator

• It is mechanical comparator providing magnification in the range of 300 to 5000.

• It consist of a plunger mounted on two flat steel string.

• This provide frictionless linear movement.

• The plunger carries the knife edge which bear upon the face of mounting blocks of cross strip hinge.

• The moving block carries a light metal y- forked arms and wrapped around the smalldrum.

• A thin phosphors bronze ribbon is fastened to the end of the forked arms and wrapped around the small drum, mounted on the spindle carrying the pointer.

• Any vertical movement movement of the plunger and hence that of the knife edge makes the moving block of the cross strip lever to pivot.

• This cause the rotation of the y-arms.• The metallic band attached to the arms makes

the driving drum hence the pointer to rotate.

• Total magnification of the instrument is

L/a = l/r