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Metal Oxide Semiconductor (Solid State)
- Advantages
- Solid state sensors are inexpensive.
- Can be used to measure combustible gases with less oxygen present than catalytic sensors.
- Disadvantages -
- Not selective to a specific gas (Broad Range)-
- Effective over a limited range relative humidity.
- Examples of Instruments:
- Internaltion Sensor Technology IQ-1000
Selectivity is poor, but it can be modified slightly by changing the operating temperature and
by doping the tin oxide with various elements. The chief limitations concerning use of this kind
of sensor are the difficulty in the interpretation of positive readings, the potential for false
positive alarms, and the effects of humidity on sensor output. As humidity increases sensor output
increases as well. As humidity drops to very low levels, sensor output may fall to zero even in
the presence of gas.
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