Air micrometer

Claim 1

In an air micrometer including a main pipe line having an end connected to an air pressure source and another end branching off to a first branch pipe line and a second branch pipe line, said first branch pipe line extending through a first adjustable orifice valve and a zero adjusting valve to outer air, said second branch pipe line extending through a second adjustable orifice valve to a measurement head, said first branch pipe line branching off at the outlet side of said first orifice valve to an inlet of a differential pressure transducer and connecting thereto, said second branch pipe line branching off at the outlet side of said second orifice valve to another inlet of said transducer and connecting thereto, the output terminal of said transducer being connected to the input terminal of a direct current amplifier for the indication of differential pressure between outlet sides of said first and second orifice valves; the improvement which comprises said second branch pipe line second orifice valve outlet side branching off to first and second subbranch pipe lines, said first subbranch pipe line extending through a first stop valve to a standard measuring head to be applied to a standard gauge, said second subbranch pipe line extending through a second stop valve to said measurement head to be applied to a workpiece to be measured, an output correction circuit connected to said amplifier, first and second output terminals, and a changeover switch for selectively connecting said first and second output terminals to the input terminal of an indicator, said first output terminal being connected through a variable resistor to said amplifier output terminal, and said second output terminal being connected to said output correction circuit output terminal, said output correction circuit including a circuit means for eliminating said amplifier output, a circuit means for passing said amplifier output through said output correction circuit, and a switch means for selectively connecting said former and latter circuit means between said amplifier output terminal and said second output terminal, said circuit for eliminating said amplifier output is a differentiation circuit, said circuit for passing said amplifier output is said differentiation circuit and an integration circuit connected in series, and said switch means for selectively connecting said former and latter circuits is connected in parallel to said integration circuit.