Measuring and testing – Fluid pressure gauge – With pressure and/or temperature compensation
Patent
1985-08-28
1987-02-24
Woodiel, Donald O.
Measuring and testing
Fluid pressure gauge
With pressure and/or temperature compensation
73718, 73724, 331 65, 361283, G01L 708, G01L 912, G01L 1904, C08C 1910
Patent
active
046447989
ABSTRACT:
A capacitive type converter device, such as used for measuring pressure, comprising first and second rectifying circuits, each including an operational amplifier with a non-inverting input terminal connected to a reference point, to which a variable condenser is connected, the variable condenser having a capacitance which varies in response to a force being measured, such as pressure, and to which a reference condenser is connected, the reference condenser having a capacitance which is fixed independent of the force being measured. The device further comprises an oscillator, whose oscillation output is applied to the variable and reference condensers,and which is controlled by a control means in response to output of the first rectifying circuit, or in response to the output of the second rectifying circuit together with the output of the first rectifying circuit, whereby an output responsive to the capacitance of the variable condenser is obtained from the output of the second rectifying circuit, or an output relating to the difference between the capacitances of the condensers is obtained from the outputs of the first and second rectifying circuits. The device eliminates adverse influences of stray capacitances, non-linearity, offset signals, and parallel capacitances and forward voltages.
REFERENCES:
patent: 4357834 (1982-11-01), Kimura
patent: 4391146 (1983-07-01), Grindheim
patent: 4586108 (1986-04-01), Frick
Hirata Terutaka
Odohira Tetsu
Ogawa Tadahiro
Tamura Hisashi
Kojima Moonray
Woodiel Donald O.
Yokogawa Hokushin Electric Corporation
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