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Device for and use of Gas Concentration Monitoring

IP.com Disclosure Number: IPCOM000234026D
Publication Date: 2014-Jan-08

Publishing Venue

The IP.com Prior Art Database

Abstract

A sensor (10) and methods for monitoring a parameter relating to the concentration of a fluid components is described with one or more heat sources (15) and at least one detector (16,17) for measuring a quantity related to temperature with the at least one detector (16,17) being located at a fixed distance from the one or more heat sources (15), and a humidity sensor (22) spatially separated from the one or more heat sources (15) and at least one detector (16,17) while being exposed to essentially the same fluid.

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Device for and Use of Gas Concentration Monitoring

Abstract

          A sensor (10) and methods for monitoring a parameter relating to the concentration of a fluid compo- nents is described with one or more heat sources (15) and at least one detector (16,17) for measuring a quantity related to temperature with the at least one detector (16,17) being located at a fixed distance from the one or more heat sources (15), and a humidity sensor (22) spa- tially separated from the one or more heat sources (15) and at least one detector (16,17) while being exposed to essentially the same fluid.

Technical Field

          The present invention relates to a gas con- centration monitor based on thermal conductivity and re- lated methods to improve the accuracy of such gas concen- tration measurements.

Background of the Invention

          Various devices are known which use the heat transfer between a heated element such as a wire and a fluid flowing around the heated element to determine flow properties and material properties of the flow compo- nents. Examples of such devices include the so-called Pi- rani gauge. Other examples use a heat source located be- tween two temperature probes to determine flow rates and composition parameters.

          In the United States patent US 7360396 B2 a method is described a gas sensor where an arithmetic unit


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calculates humidity based on the difference between standardized output values, and corrects the standardized outputs based on the calculated humidity and humidity correction equations.

          In the light of the above it can be seen as a task of the present invention to improve the performance of gas concentration sensors based on thermal conductivi- ty.

Summary of the Invention

          In accordance with a first aspect of the in- vention there is provided a sensor to monitor the concen- tration of a gas in combination with a discrete sensor designed specifically to detect humidity and a tempera- ture sensor in the immediate vicinity of the gas sensor.

          The discrete sensor designed specifically to detect humidity is preferably a capacitive sensor. The humidity sensor can further include an integrated temper- ature sensor such that the humidity sensor can generate directly a measurement of the absolute humidity.

          The sensor is based on measuring changes of the thermal conductivity of a fluid to which the sensor is exposed. Preferably, the sensor includes one or more heat sources and at least one, but preferably two or more detectors for measuring a quantity related to temperature with the detectors being located at a fixed distance from the one or more heat sources. The detectors and heat sources together with the humidity and temperature sen- sors are preferably mounted on a single semiconductor substrate or on several pieces of semiconductor material bonded together.

          In particular, it can be advantageous to com- bine the above sensor elements with further electronic components on a single semiconductor substrate to form an integrated sen...