The sensing element is comprised of a metal oxide semiconductor layer formed on the alumina substrate of a sensing chip together with an integrated heater. In the presence of detectable gas, sensor conductivity increases depending on gas concentration in the air. A simple electrical circuit can convert the change in conductivity to an output signal which corresponds to the gas concentration.
The TGS 2602 has high sensitivity to low concentrations of odorous gases such as ammonia and H2S generated from waste materials in of ce and home environments. The sensor also has high sensitivity to low concentrations of VOCs such as toluene emitted from wood nishing and construction products. Figaro also offers a microprocessor (FIC02667) which contains special software for handling the sensor's signal for appliance control applications.
Due to miniaturization of the sensing chip, TGS 2602 requires a heater current of only 42mA and the device is housed in a standard TO-5 package.
The gure below represents typical sensitivity characteristics, all data having been gathered at standard test conditions (see reverse side of this sheet). The Y-axis is indicated as sensor
- resistance ratio (Rs/Ro) which is de ned as follows:
- Rs = Sensor resistance in displayed gases at various concentrations
- Ro = Sensor resistance in fresh air
The gure below represents typical temperature and humidity dependency characteristics. Again, the Y-axis is indicated as sensor resistance ratio (Rs/Ro), de ned as follows:
- Rs = Sensor resistance in fresh air at various temperatures/humidities
- Ro = Sensor resistance in fresh air at 20°C and 65 R.H.
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