Diagnostic method and apparatus for solid electrolyte gas analyzer
First Claim
1. A gas analyzer having a solid electrolyte cell and a heater disposed proximate the cell, the cell providing a cell output as a function of a gas of interest, the gas analyzer providing an analyzer output as a function of the cell output and comprising:
- a heater circuit coupled to the heater to heat the cell in response to a control signal;
a temperature sensitive device operably coupled to the cell and adapted to provide a temperature sensitive device output related to temperature of the cell;
a measurement circuit coupled to the cell and including a diagnostic circuit to measure an impedance of the cell and provide a diagnostic output indicative of a cell degradation condition while the cell is exposed to the gas of interest;
a controller coupled to the diagnostic circuit adapted to intermittently activate the diagnostic circuit, receive the temperature sensitive device output, and provide the control signal to the heater circuit to maintain the cell at an elevated temperature; and
a memory circuit adapted to store diagnostic information relating cell impedance to cell degradation, and wherein the diagnostic output is related to the diagnostic information and cell impedance.
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Accused Products
Abstract
A solid electrolyte gas analyzer is equipped with a diagnostic circuit that intermittently measures an impedance of the solid electrolyte measurement cell as an indication that the cell is in need of calibration or replacement. The diagnostic operation is performed on the cell in situ, i.e., while the solid electrolyte cell is exposed to the gas to be measured and heated to a controlled elevated temperature. Preferably the cell impedance is measured at a predetermined frequency by injecting a modulated current through the cell and measuring the resulting voltage drop.
89 Citations
18 Claims
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1. A gas analyzer having a solid electrolyte cell and a heater disposed proximate the cell, the cell providing a cell output as a function of a gas of interest, the gas analyzer providing an analyzer output as a function of the cell output and comprising:
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a heater circuit coupled to the heater to heat the cell in response to a control signal; a temperature sensitive device operably coupled to the cell and adapted to provide a temperature sensitive device output related to temperature of the cell; a measurement circuit coupled to the cell and including a diagnostic circuit to measure an impedance of the cell and provide a diagnostic output indicative of a cell degradation condition while the cell is exposed to the gas of interest; a controller coupled to the diagnostic circuit adapted to intermittently activate the diagnostic circuit, receive the temperature sensitive device output, and provide the control signal to the heater circuit to maintain the cell at an elevated temperature; and a memory circuit adapted to store diagnostic information relating cell impedance to cell degradation, and wherein the diagnostic output is related to the diagnostic information and cell impedance. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. In a gas analyzer having a solid electrolyte cell heated by a heater and coupled to an analyzer circuit, the solid electrolyte cell providing a cell output as a function of a gas of interest, the improvement wherein the analyzer circuit comprises:
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a heater circuit coupled to the heater; a temperature sensitive device operably coupled to the cell and the heater circuit to maintain the solid electrolyte cell at an elevated temperature sensed by the temperature sensitive device; a memory having cell related diagnostic information stored therein; and a controller for controlling the memory to provide an analyzer output indicating the condition of the solid electrolyte cell as a function of a measured impedance and selected diagnostic information in the memory, said controller being operably coupled to an output of said temperature sensitive device. - View Dependent Claims (9)
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10. A method of detecting a condition of a solid electrolyte cell providing a cell EMF in response to an amount of constituent in a gas of interest exposed to the cell, the method comprising the steps of:
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(a) maintaining the cell at an elevated temperature; (b) measuring the cell EMF and providing as a function thereof an analyzer output indicative of the amount of constituent; (c) measuring a cell diagnostic parameter while the cell is exposed to the gas of interest and maintained at the elevated temperature and providing as a function thereof a diagnostic output indicative of the condition of the cell; (d) storing in memory a mathematical model of the cell diagnostic parameter as a function of time; (e) revising the mathematical model using the measured cell diagnostic parameter; and (f) using the revised mathematical model to generate the diagnostic output. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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Specification