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Detection Principles

Detection Principles

Electrochemical (EC)

An electrochemical sensor consists of a chamber with two or three electrodes and an electrolyte. A membrane, such as a porous PTFE-sheet, prevents the electrolyte from leaving the chamber.

Chemosorption (CS)

In chemosorption, the sensor element is integrated with a diplexer. The sensor element has the ability to change its electrical resistance depending on surrounding gas concentrations.

Charge Carrier Injection (CI)

The CI-sensor consists of special gas sensitive material that has the ability to bound ammonia to itself. By absorbing NH3 molecules the “Charge Carriers” of the ammonia is injected into the new sensor material (Injection).

Catalytic Combustion (CC)

The measuring and warning devices for explosive gases and vapours primarily use the catalytic combustion measuring principle. The catalytic combustion measurement is performed with the help of a “Wheatstone bridge”.

Infrared (IR)

The infrared measurement principle utilizes the characteristic of gas to absorb light in some defined wavelength ranges (bands). Heteroatomic gases such as CO2, CH4, NO2, and C2H2 can be measured with infrared sensors.

Thermal Conductivity (TC)

Thermal conductivity is used to measure gas concentrations up to 100% volume. Thermal conductivity is suitable for measuring combustible and toxic gases. It is, however, not suitable for monitoring in the LEL range.

Zirconium oxide (ZD)

This method is proper for the detection in percent range and in particles per million (ppm). The response time of the oxygen sensor is very quick and the detection principle features a good long time stability and selectivity.


GfG sets uncompromising standards in gas detection and sensor technology for measuring and warning of potentially hazardous environments. Over 500 gases can be monitored with GfG transmitters. The gases are divided into three groups: EX, OX, and TOX.

Combustible Gases (EX)

All combustible and explosive gases are combined under the term “EX.” The LEL range (Lower Explosion Limit) is measured in ppm.

Oxygene (OX)

“OX” stands for oxygen. Detection normally serves to monitor the air we breathe, and is measured in % volume (the oxygen in air = 20.9% volume).

Toxic Gases (TOX)

“TOX” describes all poisonous (toxic) gases. These gases are generally monitored for personal protection; for example, monitoring the TLV (Threshold Limit Value). The range is measured in ppm.