TGS2442 Datasheet, PDF (7/25 Pages) List of Unclassifed Manufacturers – Detection of Carbon Monoxide

TECHNICAL INFORMATION FOR TGS2442
3. Basic Sensitivity Characteristics
3-1 Sensitivity to various gases
100
Air
Ethanol
Figure 7 shows the sensor’s relative sensitivity to
10
various gases. The Y-axis shows the ratio of sensor
H2
resistance in various gases (Rs) to the sensor
resistance in 100ppm of CO (Ro).
1
As shown by Figure 7, TGS2442 shows very good
sensitivity to CO since the sensitivity curve to CO
shows a sharp drop in sensor resistance as CO
concentration increases. In comparison, sensitivity
to ethanol (C2H5OH) is very low as evidenced by the
relatively flat slope of its sensitivity curve and high
resistance values.
0.1
0.01
1
CO
10
100
1000
10000
The amount of CO␣ generated by cigarette smoke is
roughly equivalent to 20ppm of CO when 10
cigarettes are smoked in a room of roughly 24 cubic
meters in size. As a result, the influence of cigarette ₁₀₀₀
smoke itself would not be sufficient to cause the
sensor to generate an alarm for residential detectors
using TGS2442 which are normally calibrated to ₁₀₀
alarm at 100ppm of CO.
Gas Concentration (ppm)
Figure 7 - Sensitivity to various gases
(Ro = Rs in 100ppm of CO)
50%RH
Air
10
3-2 Temperature and humidity dependency
Figure 8a shows the temperature dependency of
TGS2442. The Y-axis shows the ratio of sensor
resistance for various CO concentrations under
various temperature conditions (Rs) to the sensor
resistance in 100ppm of CO at 50%RH (Ro).
Figure 8b shows the humidity dependency of
TGS2442. The Y-axis shows the ratio of sensor
resistance for various CO concentrations under
various relative humidity conditions (Rs) to the
sensor resistance in 100ppm of CO at 20˚C.
An inexpensive way to compensate for temperature
dependency to a certain extent would be to
incorporate a thermistor in the detection circuit (please
refer to Section 5-2).
CO 30ppm
1
CO 100ppm
CO 300ppm
0.1
-20 -10 0 10 20 30 40 50 60
Temperature (˚C)
Figure 8a - Temperature dependency at 50%RH
(Ro = Rs in 100ppm of CO at 20˚C)
100
Air
20˚C
10
CO 30ppm
1
CO 100ppm
0.1
0
CO 300ppm
20
40
60
80
100
Humidity (%RH)
Figure 8b - Humidity dependency at 20˚C
(Ro = Rs in 100ppm of CO at 50%RH)
Revised 03/00
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