High-temperature pressure sensing
First Claim
1. A pressure sensing system comprising:
- a hot zone electronics module having a capacitive pressure sensor which comprises a variable capacitor having a capacitance which changes as a function of applied pressure and a reference capacitor, and an oscillator that provides an oscillating signal to the capacitive pressure sensor, the hot zone electronics module providing at least a first DC sensor signal related to capacitance of the variable capacitor and a second DC sensor signal related to capacitance of the reference capacitor;
a cool zone electronics module that converts the DC sensor signals into a pressure value and that provides a DC power signal; and
a plurality of conductors that connect the hot zone electronics module to the cool zone electronics module and that convey the DC power signal to the hot zone electronics module, the plurality of electrical conductors including a first conductor that carries the first DC sensor signal and a second conductor that carries the second DC sensor signal, wherein the plurality of conductors comprise elongate conductors and the hot zone electronics module is located at a remote location relative to the cool zone electronics module, the hot zone electronics module comprises first and second voltage conductors which power the oscillator, a first DC conductor which carries current to the variable capacitor having a capacitance which changes as a function of applied pressure, a second DC conductor which carries current to the reference capacitor, and a difference current conductor which carries a current related to a difference in current flowing through the variable capacitor and the reference capacitor.
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Accused Products
Abstract
A pressure sensing system includes a hot zone electronics module, a cool zone electronics module and a plurality of conductors that connect the hot zone electronics module to the cool zone electronics module. The hot zone electronics module includes a capacitive pressure sensor and an oscillator that provides an oscillating signal to the capacitive pressure sensor. The hot zone electronics module provides at least one DC sensor signal. The cool zone electronics module converts the at least one DC sensor signal into a pressure value and provides a DC power signal. The plurality of conductors convey the DC power signal to the hot zone electronics module and convey the at least one DC sensor signal to the cool zone electronics module.
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Citations
24 Claims
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1. A pressure sensing system comprising:
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a hot zone electronics module having a capacitive pressure sensor which comprises a variable capacitor having a capacitance which changes as a function of applied pressure and a reference capacitor, and an oscillator that provides an oscillating signal to the capacitive pressure sensor, the hot zone electronics module providing at least a first DC sensor signal related to capacitance of the variable capacitor and a second DC sensor signal related to capacitance of the reference capacitor; a cool zone electronics module that converts the DC sensor signals into a pressure value and that provides a DC power signal; and a plurality of conductors that connect the hot zone electronics module to the cool zone electronics module and that convey the DC power signal to the hot zone electronics module, the plurality of electrical conductors including a first conductor that carries the first DC sensor signal and a second conductor that carries the second DC sensor signal, wherein the plurality of conductors comprise elongate conductors and the hot zone electronics module is located at a remote location relative to the cool zone electronics module, the hot zone electronics module comprises first and second voltage conductors which power the oscillator, a first DC conductor which carries current to the variable capacitor having a capacitance which changes as a function of applied pressure, a second DC conductor which carries current to the reference capacitor, and a difference current conductor which carries a current related to a difference in current flowing through the variable capacitor and the reference capacitor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 22)
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13. A sensor apparatus comprising:
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sensor electronics comprising an oscillator, and a capacitive sensor providing two DC signals related to a process variable and a reference; conversion electronics located remotely from the sensor electronics that use at least two DC signals from the sensor electronics to form a value for a process variable; and an elongate multi-conductor cable comprising at least two conductors that provide the at least two DC signals from the sensor electronics to the conversion electronics, wherein one of the at least two conductors carries a first DC sensor signal and the second of the at least two conductors carries a second DC sensor signal, and wherein the sensor electronics comprise first and second voltage conductors which power the oscillator in a hot zone electronics module, a first DC conductor which carries current to a variable capacitor of the sensor electronics, the variable capacitor having a variable capacitance which varies as a function of applied pressure, a second DC conductor which carries current to a reference capacitor of the sensor electronics, and a difference current conductor which carries a current related to a difference in current flowing through the variable capacitor and the reference capacitor. - View Dependent Claims (14, 15, 16, 17, 18, 23)
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19. A method comprising:
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forming at least two DC sensor signals using a diode detector at a temperature greater than 200 degrees Celsius, the at least two DC sensor signals comprising a first DC sensor signal related to a sensed process variable and a second DC sensor signal related to a reference; conveying the at least two DC sensor signals across an elongate multi-conductor cable to process variable calculation electronics located remotely from the diode detector by applying the first DC sensor signal to a first conductor and a second DC sensor signal to a second conductor of the multi-conductor cable, wherein the diode detector comprises first and second voltage conductors which power the oscillator in the diode detector, a first DC conductor which carries current to a variable capacitor in the diode detector, the variable capacitor having a variable capacitance which varies as a function of applied pressure, a second DC conductor which carries current to a reference capacitor in the diode detector, and a difference current conductor which carries a current related to a difference in current flowing through the variable capacitor and the reference capacitor; converting the at least two DC sensor signals into a process variable value using the process variable calculation electronics at a temperature below 100 degrees Celsius. - View Dependent Claims (20, 21, 24)
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Specification