Hibrid Pressure Cascade Pneumatic Micrometer

Abstract

Although ordinary pneumatic micrometers with higher gauge pressures are most adaptable types for industrial measuring instruments, they have comparatively large measuring force and have little linear parts in their transfer characteristics. Described in this paper is a method for improvement of performances of the pneumatic micrometers.
Trially manufactured apparatus is composed of two single pneumatic micrometer circuits, one, lower pressure type pneumatic micrometer having a jet nozzle held by a spring-bellows transducer for negative feedback, serves as a preamplifier, and the other, higher pressure type pneumatic micrometer single circuit connected in cascade to the former through a pressure displacement transducer, serves as an output amplifier.
The transfer amplification factors are given as K^*/S when K^* is a spring constant of the feedback transducer and S is a bellows effective area of pressure. Experiments conducted by using spring assembly, which is composed of eight compression springs, proved that more than 93% range of full scale is linearised with accuracy of less than 1 % in its static transfer characteristics and measurement under constant low measuring force less than 2g is performed. Also discussed are dynamic characteristics and the effects upon changing the circuit components.