Sensor Detects Cable Fire Before It Starts
Engineering360 News Desk | December 01, 2015Scientists at the Karlsruhe Institute of Technology (KIT) and Karlsruhe University of Applied Sciences have developed a sensor that can detect a fire before it begins by analyzing the plastic vapors released by overheated insulating cables.
To develop the sensor, researchers—led by Dr. Heinz Kohler, of the Institute of Sensor Technology and Information Systems (ISIS) of the Karlsruhe University of Applied Sciences, and Dr. Hubert Keller, Simulation and Measurement Project Head of KIT’s Institute for Applied Computer Science—studied how various gases react with gas-sensitive metal oxides as a function of temperature.
The sensor comprises four areas with different metal oxides that change temperature-dependent electric resistance when in contact with gases. Image credit: KIT/HsKA.“This effect is the basis of a self-heated, temperature-controlled sensor chip with four sensors, i.e., a sensor array," Kohler says. The array is heated cyclically and cooled down again. Simultaneous measurement of electric resistance or conductance yields four specific conductance signatures, the evaluation of which provides information on the composition and concentration of the gas.
Insert image here: The researchers found that the array was able to yield conductance signatures appropriate to identify specific gases. The sensors detected and identified pyrolysis gas emissions at relatively low sample heating temperatures even before a visible color change of the polyvinyl chloride (PVC)-isolation material. The dynamic conductance signals were evaluated using SimSens, a numerical analysis tool designed for simultaneous evaluation of conductance profiles.
According to the researchers, the results show promising pyrolysis gas identification and concentration determination capabilities in relation to the conductance profile shapes of model gases like carbon monoxide and propene, which help to prevent false alarms.
In addition to increasing the safety of cable ducts, the researchers say the sensors' capacity to find gas mixtures and determine individual gas concentrations could be useful in detecting toxic mold gases during food control, explosive gases in fertilizer silos or leaks of natural gas pipelines.
“Hybrid sensors can be used anywhere as separate systems or in a network," says Keller. "They may also be combined with classical safety technology, such as infrared cameras."