Technical Information
SB and SP Type Gas Sensors
Sensing material structure is different between SB and SP types.
SB (Semiconductor Bead) type sensing element is a mini bead type semiconductor mainly composed of tin-dioxide (SnO2). A heater coil and an electrode wire are embedded in the element. This structure realizes large reduction of power consumption and quick response.
SP (Semiconductor Plate) type sensing element is formed on the alumina substrate on which the gold electrodes are printed. A thick film heater of ruthenium-oxide or platinum is printed on the reverse of the substrate. Variations of sensing materials and its thickness controllability have led to improvements in sensor performance and wide variation in the product range.
SP type sensing element
Detection Principle of Semiconductor Gas Sensor
The conductivity of tin dioxide (SnO2) metal oxide semiconductor materials changes according to gas concentration changes.
This is caused by adsorption/desorption of oxygen and reaction between surface oxygen and gases.
These reactions cause a dynamic change of electric potential on SnO2 crystal and results in the decrease of sensor resistance under the presence of reducing gases such as CO, methane, hydrogen.
