5 different types of gas sensors widely used are:
- Solid State
- Infrared
- Photoionization
- Catalytic Bead
- Electrochemical
This gives you the flexibility to choose the best sensor(s) for your particular application. A brief description of each sensor type follows:
SOLID STATE
Solid State sensors are made of a heated metal oxide material which temporarily changes resistance in the presence of gas. Solid State sensors are available for the detection of over 150 different toxic and combustible gases, in ranges from low ppm %LEL. A list of gases and ranges appears on the back of this brochure. Solid State sensors come with a 3 year warranty, and have a life expectancy in excess of 10 years.
INFRARED SENSOR (IR)
Infrared (IR) sensors detect gases that absorb light in the infrared spectrum. Sensors for carbon dioxide (CO2), carbon monoxide, and hydrocarbons (such as Methane, etc.) are currently available. IR sensors offer good selectivity and good lifetimes. Ranges for CO2 are available from ppm to 20% by volume, with the lower ranges offering better resolution. CO is available in % volume ranges, and hydrocarbon ranges are available from %LEL up to 100% by volume, depending upon the gas.
PHOTOIONIZATION DETECTOR (PID)
Photoionization detectors (PID) operate by ionizing the target gas with ultra-violet radiation, and then collecting the ions across a high voltage plate which produces an electrical signal proportional to the gas present. PID’s offer fast response for many Volatile Organic Compounds (VOC’s), including, among others, benzene, vinyl chloride, phosphine, and hexane.
ELECTROCHEMICAL
Electrochemical sensors operate by producing a chemical reaction with the gas of interest. Sensors are available for certain toxic gases in ppm ranges, including NH3, CO, Cl2, H2, HCl, HCN, H2S, NO, NO2, O2, O3, and SO2. For some of these gases, electrochemical sensors can offer a fairly high degree of selectivity. Electrochemical sensors have a life expectancy of 1 to 2 years and come with a 1year warranty.
CATALYTIC BEAD
Catalytic Bead sensors operate by burning combustible gases, raising the temperature of the sensor. This temperature rise changes the resistance of the sensor and produces a signal proportional to the gas concentration. They detect combustible gases in higher concentrations (above 1000 ppm) only. They are not selective and will respond to a wide range of combustible gases. However, since they only detect higher gas concentrations, they are not prone to interference from many toxic gases. Catalytic Bead sensors have a life expectancy of 2 years and come with a 1 year warranty.
