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SC2-AT6 – UserManual
Specifications subject to change without notice. | Tox_D_1119, Ex_D_1119, CO2_D_0320 | USA 200413 | Page 4 of 17
1.5 Sensor Element for Combustible Gases
The integrated sensor works according to the catalytic bead principle. The ambient air to be monitored diffuses through
a sintered metal disk into the sensor. Here the combustible gases and vapours are burned catalytically at a heated
detector element (pellistor). The resulting combustion heat also heats up the detector element. This heating changes
the resistance of the detector element which is proportional to the partial pressure of the combustible gases.
In addition to the catalytic detector element, the sensor also has a similarly heated inactive compensator element.
Both elements are part of a Wheatstone measuring bridge. Environmental influences such as temperature, air humidity
or thermal conductivity of the ambient air to be monitored affect both elements to the same extent so that these
influences have no significant effect on the measuring signal.
Certain substances and gases in the ambient air to be monitored can affect the sensitivity of the sensor
element or destroy the sensor completely. This is called poisoning.
The following are currently known:
•
Polymerising substances, such as ethylene oxide, acrylonitrile, butadiene, styrene, silicone.
•
Corrosive substances, such as halogenated hydrocarbons.
•
Catalytic poisons, such as sulphur and phosphor compounds, silicon compounds, metal vapours.
•
Organic solvents
For testing the sensor, do not use a lighter. If gassed with a lighter the sensor cannot be employed for reliable
measurement and must first be recalibrated. The sensor may be damaged, and the calibration should then be
repeated at much shorter intervals. In addition, the resulting amount of heat can lead to the mechanical destruction of
the sensor. The product warranty is void by fumigation with a lighter.
1.6 Infrared Sensor Element for CO
The integrated sensor is based on the principle of the infrared absorption of gases and accomplishes highest
requirements concerning accuracy, reliability and economy. The sensor technology uses the individual absorption
spectrum of the carbon dioxide gas and determines its exact concentration through its accurate, quantitative analysis.
The infrared principle nearly eliminates the cross-sensitivity to other gases.
An integrated evaluation electronic system reliably compensates all drift and temperature influences and therefore a
genuine measurement result is guaranteed.
Certain substances and gases in the monitored ambient can affect the sensitivity of the sensor element
or destroy the sensor completely. This is called poisoning.
The following are currently known:
• Polymerising substances, such as ethylene oxide, acrylonitrile, butadiene, styrene, silicone
• Corrosive substances, such as halogenated hydrocarbons
• Catalytic poisons, such as sulphur and phosphor compounds, silicon compounds, metal vapours
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