Features of sensors used in gas detection. What is important and how does it influence sensor selection?

What are the characteristics of an electrochemical, catalytic, infrared (IR), or photoionization sensor? What characteristics should be considered, and what are their implications for a gas detector?

Atest Gaz Gas Detectors are equipped with appropriate sensors, selected from a wide range of available solutions depending on the application. The selection of the appropriate sensor is, of course, influenced by the type of gas being detected, the measurement range, and also the environmental conditions in which the device will operate.

Sensors we use in gas detectors:

• Electrochemical sensors

Detectors equipped with electrochemical sensors are used for measuring and detecting the presence of
specific substances in gaseous atmospheres in concentrations generally above single “ppm,” but in some
cases (e.g. oxygen, hydrogen), the concentration may be tens or hundreds of thousands “ppm”.
These gases have characteristic measurement ranges. Most of the detected substances are primarily volatile
inorganic compounds. Some organic compounds, such as ethylene, ethylene oxide, may also be detected.

• Catalytic sensors

Detectors equipped with catalytic sensors are used for measuring and detecting the presence of gases and
flammable gases in the range of up to 100% LEL.

• Photoionization sensors PID

Detectors equipped with photoionization sensors are used for measuring and detecting the present gas
substances, whose energy of ionization is lower then 10.6 eV. They are mostly volatile organic compounds
(VOC).

Examples of VOCs that can be detected by a PID sensor equipped with a 10.6 eV lamp:

• Aliphatic hydrocarbons – e. g. pentane, octane, hexane,
• Aromatic hydrocarbons – e. g. toluene, xylene, benzene,
• alcohols – e.g. ethanol, propanol,
• aldehydes, ketones, esters,
• amines, sulphides,
• others, including: aviation fuels, petrol, and some inorganic compounds.

PID sensors can also be equipped in e. g.: a 11.7 eV lamp, which, besides the substances enumerated above,
is able to detect such substances as: methanol, acetylene or formaldehyde. This lamp has a very short life
span (approx. 1 week).

• IR sensors

NDIR sensors (non-dispersive infra-red sensor), commonly called IR sensors, are used for measuring gases
concentrations which have ability to absorb the electromagnetic spectrum in the infra-red range:

• organic compounds particularly methane,
• carbon dioxide,
• other (e. g. carbon monoxide, nitrogen compounds, ammonia, CFC, SF6)

Those sensor do not detect hydrogen.

We invite you to read the manual, where you can find information about the principle of operation, the influence of environmental conditions and other important aspects affecting the correct operation of the sensor: