基本信息
摘要：1,199,075. Fluid-flow meters, electrical. NORTH AMERICAN ROCKWELL CORP. July 31, 1967 [July 29, 1966], No.35150/67. Heading G1N. A flowmeter for insertion in a fluid-flow line comprises semi-conductor strips 19, 29 (Fig.1) having Piezo-resistive semi-conductor strain gauges 20, 30 formed thereon by bonding, planar diffusion, or epitaxial growth. The strips may be N-type while the strain gauges are P-type or vice-versa. Each gauge is formed on a face of a respective strip so that deflection of the strips by a flowing fluid produces tensile stress in one gauge and compressive stress on the other. Where the strips cross one another a bead of epoxy resin is provided therebetween as insulation and to prevent relative movement of the strips. The gauges may be connected in a Wheatstone bridge Fig.3 (not shown). The output voltage of which is proportional to the product of the fluid density, the fluid velocity squared, and a calibration constant; and is connected to a meter which indicates flow-rate. The semi-conductor material of the strips or gauges may be silicon, germanium or carbon or other tetravalent element doped with arsenic, antimony, bismuth or phosporous to give N-type or with impurity such as aluminium indium, gallium, or boron to give P-type. Alternatively the semi-conductor strips may not be doped with impurity.
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