Measuring and testing – Fluid pressure gauge – With pressure and/or temperature compensation
Patent
1984-01-05
1985-11-05
Woodiel, Donald O.
Measuring and testing
Fluid pressure gauge
With pressure and/or temperature compensation
73718, 73724, G01L 1904
Patent
active
045506116
ABSTRACT:
An electronic pressure transducer for providing a pressure-indicative analog output signal includes a capacitive pressure sensing oscillator having a frequency dependent on an applied pressure. A combining circuit combines the oscillator signal with a constant frequency signal generated by a reference oscillator to generate a difference signal having a duty cycle dependent on the frequency difference between the oscillator signals. The difference signal is applied to an integrating circuit and amplified by a variable-gain output amplifier to develop the pressure-indicative analog output signal. A pair of D-type flip-flops and an EXCLUSIVE OR logic gate in the combining circuit enable the combining circuit to function with oscillator frequency ratios of 1:1 to 2:1, thereby enabling the capacitive pressure sensing element of the pressure sensing oscillator to operate over a wider range of sensitivities. Non-linearities at the output of the integrating circuit are compensated for by a linearizing transistor having main electrodes coupled to a degenerative feedback network in the output amplifier. A second transistor having main electrodes coupled to the control electrode of the linearizing transistor compensates for temperature variations in the conduction level of the linearizing transistor.
REFERENCES:
patent: 3841150 (1974-10-01), Pearson
patent: 3970966 (1976-07-01), Keller et al.
patent: 4165653 (1979-08-01), Morehouse
patent: 4176557 (1979-12-01), Johnston
patent: 4202218 (1980-05-01), Romo
patent: 4227419 (1980-10-01), Park
patent: 4250452 (1981-02-01), Gray
patent: 4289035 (1981-09-01), Lee
patent: 4392382 (1983-07-01), Myers
Motorola Schematic 63C44378F01.
Motorola Data Book Aug., 1973, pp. 65-68, on MC12000.
Handbook of Microcircuit Design Applications, by David Stout, page covering D Flip Flop Synchronized One Shot.
Melamed Phillip H.
Motorola Inc.
Woodiel Donald O.
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