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The catalytic bead sensor consists of two coils of fine platinum wire each embedded in a bead of alumina, connected electrically in a Wheatstone bridge circuit. One of the pellistors is impregnated with a special catalyst which promotes oxidation whilst the other is treated to inhibit oxidation. Current is passed through the coils so that they reach a temperature at which oxidation of a gas readily occurs at the catalysed bead .
Passing combustible gas raises the temperature further which increases the resistance of the platinum coil in the catalysed bead, leading to an imbalance of the bridge. This output change is linear, for most gases, up to and beyond LEL, response time is a few seconds to detect alarm levels , at least oxygen by volume is needed for the oxidation.
A catalytic bead LEL sensor senses a combustible gas through flameless combustion that occurs with the help of electrically produced heat and a catalyst material coating on the sensing bead.
In other words, a CB LEL sensor detects gas through the actual burning of the gas.Decreased sensitivity may occur depending on operating and ambient conditions , which include poisoning and sinter blockage, they become apparent during routine maintenance checking.
The Global Catalytic bead sensor market accounted for $XX Billion in 2023 and is anticipated to reach $XX Billion by 2030, registering a CAGR of XX% from 2024 to 2030.
MPS Catalytic Bead Sensor and NDIR Sensor – CAT sensors have been in use for nearly 100 years. They are popular because they are sensitive to nearly all hydrocarbons, and they are relatively inexpensive. These sensors contain two small beads, one of which is coated with a chemical catalyst while the other has an inert material.
When powered on, the beads are heated to a high temperature. If hydrocarbon gas(es) reach the sensing element, the catalyst-coated bead heats up more than the inert one, and the temperature difference can be measured. This temperature difference provides a reading relative to the concentration of the flammable gas present.
And while this is a tried-and-true method of gas detection, there are certain limitations with catalytic bead sensors. They are prone to ‘poisoning,’ which occurs when the sensor comes into contact with higher hydrocarbons, alcohols, ketones, esters, hydrogen sulfide and other sulfur containing compounds.
Poisoned sensors often appear to be operating normally – which is an incredibly unsafe hazard for individuals in the area who may be inadvertently exposed to dangerous gases.
Calibration of these sensors is also challenging since if it is calibrated to a single gas, the sensor will output inaccurate readings for all other gases.
