Workshop - What to Look for in Gas Detection and Measurement Instrumentation (40)

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Slide 40 of 76

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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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