In many chemical processes, it is often desirable to detect the presence, quantity, and/or qualities of certain chemicals of interest; for example, in many closed chemical processes (either batch or continuous), the generation or infiltration of certain deleterious chemicals can damage or ruin the effectiveness of the process. By continually or periodically monitoring such processes, the presence and/or amount of a deleterious chemical may be timely reported, and damage to the system may be averted.

The sensor allows a specific gas or chemical to be specifically identified, but also can determine its concentration, mass, temperature, and time history.

One difficulty in monitoring certain chemical processes is that such monitoring may in itself have a negative effect on a system being monitored. The presence of a monitoring device may interrupt system flow or adversely affect system output quality. Often, negative effects associated with certain monitoring equipment are due to the size of the monitoring equipment or the requirement of actively interjecting such monitoring equipment into a system from outside the system. Additionally, many chemical monitor devices or monitoring systems are limited in that only the presence of a particular chemical may be indicated, as opposed to indicating quantity and/or quality information.

There is a need for chemical sensors that are capable of passively monitoring a particular application in-situ so that the application is substantially unaffected by the presence of the sensor. Also needed are chemical sensors and/or sensor systems capable of generating accurate and detailed quantification information based on differences in temperature gradients over time, and in-situ chemical sensors capable of indicating a threshold event using an expendable and very small sensing apparatus.

A chemical sensor was developed for assessing a chemical of interest. The chemical sensor includes two thermocouples. A reactive component is typically disposed near the second thermocouple, and is selected to react with the chemical of interest and generate a temperature variation that may be detected by a comparison of a temperature sensed by the second thermocouple, compared with a concurrent temperature detected by the first thermocouple.

The sensor can be used as a passive or active detector. It allows a specific gas or chemical to be specifically identified, but also can determine its concentration, mass, temperature, and time history. The sensor provides quantitative analysis for determining longevity of the system.

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Tech Briefs Magazine

This article first appeared in the July, 2018 issue of Tech Briefs Magazine.

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