A hinged cross strip is present in sigma comparator which has a fixed and a moving member. These are connected to by thin flexible strips and right angle to each or. External force is applied on moving member.

Pneumatic gauge can be used for parts of diameter 0.5 mm to 900 mm having tolerance 0.05 mm or less. It can be easily used for on line measurement of parts.

Automatic gauging machines are most accurate among m. These are similar to multicheck devices and incorporate comparator amplifying methods. Less skilled operator is required as all inspection is done automatically.

Mechanical and optical magnification of this instrument is of order of 400 and 50 respectively. Thus, overall magnification of Eden-rolt millionth comparator is of order of about 20,000.

Pneumatic sensitivity in pneumatic comparator is directly dependent upon operating pressure and inversely proportional to geometrical area of orifice. It can be represented as dp/dM.

In air multicheck comparators, group of air comparators are used. It is difficult to set se comparators initially to check various dimensions and to arrange m in compact form. But once this set up is done, or things become very easy.

Zeiss ultra-optimeter gives a high degree of magnification. This instrument has an optical system involves a double reflection of light. A green filter is present which filters all but green light which is less fatiguing to eye.

Upstream pressure and pressure between both orifices, y both are measured with reference to atmospheric pressure. The relationship between both pressures depends upon relative sizes of two orifices.

Sigma comparator is a mechanical comparator. Components of sigma comparator are a plunger, knife edge, cross strip hinge, Y-shaped arm, driving drum, slit diaphragm, a scale and a pointer etc.

Electrical multi check comparator is a combination gauge. 20 or more electrical-check heads are incorporated in electrical multi check comparator to measure a number of dimensions simultaneously.