Measuring and testing – Fluid pressure gauge – Diaphragm
Patent
1977-06-30
1978-09-12
Woodiel, Donald O.
Measuring and testing
Fluid pressure gauge
Diaphragm
73714, G01L 910
Patent
active
041127773
ABSTRACT:
An air pressure monitor includes an electro-mechanical sensor comprising a flexible diaphragm whose deflection is proportional to the air pressure applied thereto, and a variable inductor including a coil and a movable core inside of the coil, the movable core being attached to the flexible diaphragm for movement in response to the deflection thereof to adjust the inductance of the coil in proportion to the air pressure applied to the diaphragm. The monitor further comprises electrical circuits including a first oscillator circuit including the coil for producing a pressure signal at a frequency proportional to the pressure in response to the inductance of the coil, and a second oscillator circuit for producing a reference signal at a frequency corresponding to the frequency produced by the first oscillator when the pressure is substantially zero. Mixer and filter circuits are provided, connected to the two oscillator circuits for providing a signal whose frequency is proportional to the difference in frequencies between the pressure and reference signals and a Schmitt trigger and divider are connected in series from the filter circuit for producing a chain of digital pulses at a frequency proportional to that of the difference signal. An adjustable gate generator is provided for producing a gate signal having a predetermined period, such that the number of digital pulses produced at the output of the divider during the predetermined period comprises a digital signal corresponding to a measurement in predetermined, fixed units of the pressure at the diaphragm.
REFERENCES:
patent: 3750474 (1973-08-01), Pollack
Hibberd, "Integrated Circuits" McGraw-Hill Book Co., N.Y., p. 6, 1969.
Dickey-john Corporation
Woodiel Donald O.
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