The SB-11A is a tin dioxide semiconductor gas sensor which has an excellent performance in methane, propane, butane and other hydrocarbons detection with significant low power consumption concept (120 mW). High sensitivity, low sensitivity to noise gases, quick response speed and strong poisoning resistance features achieve

reliable gas detection system applications.

Structure

Gas sensitive semiconductor material is a mini bead type and a heater coil and electrode wire are embedded in the element. The sensing element is installed in the metal housing which uses double stainless steel mesh (100 mesh) in the path of gas flow. The mesh is an anti-explosion feature (Fig 1). Operating conditions Fig 2 shows the standard operating circuit for this model. The change of the sensor resistance (RS) is obtained as the change of the output voltage across the fixed or variable resistor (RL). In order to obtain the best performance and specified characteristics, the values of the heater voltage (VH) circuit voltage (VC) and load resistance (RL) must be

within the range of values given in the standard operating conditions shown in the Specification table on

the next page.

Sensitivity characteristics Fig 3 shows the sensitivity characteristics curves of the SB- 11A (typical data). Sensitivity characteristics of the FIS gas sensors are expressed by the relationship between the sensor resistance and gas concentration. The sensor resistance decreases with an increase of gas concentration based on a logarithmic function.

The sensitivity characteristics of the SB-11A is specified by the SPECIFICATIONS following parameters.

• Sensor resistance atmethane 3000 ppm

• Sensor resistance change ratio: between methane

1000 ppm and 3000 ppm (slope) and between in air and at methane 3000 ppm. See the specification table on the next page for furtherdetails.