Self-testing and self-calibrating detector
AssigneeHoneywell International Inc.
InventorsJames Z. Liu, Andrew Wood
Life of this patent
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Abstract
A self-testing and self-calibrating detector utilizing an internally produced reference gas. A detector that is sensitive to a target analyte as well as a reference gas can be utilized. A gas releasing material, such as a heated metal hydride, releases the reference gas. The partial pressure of the reference gas is known as a temperature dependent physical property of the gas releasing material. During calibration, the material can be heated to release reference gas and a calibration measurement of the gas' partial pressure can be made and compared to an expected value. The comparison can then be utilized to calibrate the detector.
Claims11
A sensor system comprising:
- a chemical detector associated with a measurement circuit that produces a measurement of the partial pressure of a gas from the output of the chemical detector, wherein said chemical detector comprises a electrochemical cell;
- a reference gas releasing material comprising a metal hydride, wherein said reference gas releasing material releases a reference gas such that the partial pressure of the reference gas is a function of the temperature of the reference gas releasing material, wherein a heater is positioned to heat the reference gas releasing material;
- a temperature sensor positioned to measure the temperature of the reference gas releasing material and a control circuit that when activated delivers a known partial pressure of the reference gas to the chemical detector by controlling the heat generated by the heater and thereby the temperature of the reference gas releasing material;
- and
- a calibration circuit that, during calibration, activates the control circuit, reads a measurement called a calibration measurement from the measurement circuit, and produces a calibration factor by comparing the calibration measurement to an expected measurement, while the calibration circuit also, during regular operation, produces a calibrated measurement from the measurement and the calibration factor.
A method of producing calibrated gas partial pressure measurements from a chemical detector comprising the steps of:
- intermittently generating a reference gas at a known partial pressure by heating a reference gas releasing material to a known temperature with a heater;
- using a metal hydride as the gas releasing material;
- exposing the chemical detector to the reference gas at a known partial pressure;
- using an electrochemical cell as the chemical detector;
- using the chemical detector to measure the partial pressure of the reference gas during those times that the reference gas is intentionally generated and thereby producing a measurement called a calibration measurement;
- producing a calibration factor by comparing the calibration measurement and an expected measurement;
- producing a calibrated gas partial pressure measurement by applying the calibration factor to a measurement obtained from the chemical detector during those times that the reference gas is not intentionally generated;
- and
- containing the chemical detector, heater, and reference gas releasing material within a unit housing.
Dependencies are inferred from the claim text.