What operational principle does a combustible gas indicator primarily rely on?

A combustible gas indicator primarily relies on the catalytic sensor and Wheatstone bridge operational principle. In this system, the catalytic sensor detects combustible gases through a process that involves oxidation. When a combustible gas comes into contact with a heated catalyst within the sensor, it ignites, leading to a temperature increase.

This temperature change is significant because it affects the electrical resistance of the sensor. The Wheatstone bridge circuit measures this change in resistance and translates it into an electrical signal, which indicates the concentration of the combustible gas present in the environment. The ability of the catalytic sensor to reliably detect and quantify combustible gases makes it a common choice in safety monitoring equipment.

Other options refer to different principles: chemical reactions can occur in various contexts but are not specific to how most combustible gas indicators function. Electrical conductivity often pertains to different types of sensors and is not primarily the mechanism of detection in this context. Infrared temperature measurement is related to detecting heat or temperature changes rather than gas concentrations. Thus, the catalytic sensor combined with the Wheatstone bridge is the correct and specific principle that defines how a combustible gas indicator operates effectively.