Abstract
The differential pressure transducer developed by the authors is very simple in construction and extremely sensitive, with a minimum span of 1mm H2O producing an output signal of 1.5mV, even without an amplifier. Its dynamic characteristics are flat in the range betweem 0 and 15Hz.
This transducer consists of two principal assemblies:
(1) Deflection-balance assembly-consists of a casing and a slightly tightened, vertical, thin diaphragm (0.013mm thick, made of polyvinyl fluoride) which divides the casing into two symmetrical pressure chambers. There are 16 prestressed, horizontal, unbonded strain gauge filaments (8 filaments on each side of the diaphragm), which are each connected to the center of the diaphragm by means of a diaphragm disk and to the casing wall.
(2) Electrical assembly-consists of a 4-arm active Wheatstone bridge (cach arm containing 4 series-connected filaments on the side of the diaphragm), its power supply, and output terminals.
Differential pressure causes positive strain in the filaments on the side of higher pressure and negative strain on the other side. Consequently mV output is proportional to the differential pressure. Displacement of the diaphragm is as slight as 0.015mm at a differential pressure of 2.5mm H2O which serves to demonstrate its fine dynamic characteristics.
This transducer contains a temporary field checking system and can be assembled into a portable instrument, including an indicator or recorder.
