TGS2442 Datasheet, PDF (24/25 Pages) List of Unclassifed Manufacturers – Detection of Carbon Monoxide

CALIBRATION OF TGS2442
for each concentration are spelled out by the performance standards even if calibrated with only
standard. While the standard lists specific delay times one CO␣ concentration. This verification is based on
allowed for each CO␣ concentration, to facilitate this ^{the aforementioned assumptions. Any factors which}
discussion the permissible range of CO ^{may influence these assumptions should be taken}
concentrations at each specific delay time will be ^{into consideration when planning actual detector}
used.
design and when designing the calibration process.
The maximum and minimum values of alarming time
Alarm time
(tconc.) in
CO Concentration (ppm)
permitted by the standard for each CO concentration
minutes
C (min) C (center) C (max)
are plotted on the chart shown in Figure 11. The log
t65 = 103
48
65
95
center between these two curves (7.07% COHb) is
t100 = 53.6
75
100
145
also plotted. From these curves, the values of con-
t200 = 23.2
145
200
270
centration width allowed at each delay time can be
t300 = 14.9
210
300
400
determined—see Table 7 for a listing of these values.
t400 = 10.9
260
400
520
4-2 Estimation of calibration accuracy
t600 = 7.14
400
600
800
The variation in each β grade can be illustrated as in
Figure 12. The center line is based on the β center
value which is given to each sensor grade. At the
calibration point of 100ppm, the ƒ(Rs^) value of each
sensor would be the same (ƒ(Rs^) = 1.0). But at 60
and 600ppm, the ƒ(Rs^) could vary as shown in the
chart. At each concentration of CO, the center ƒ(Rs^)
can be identified and the +/- range of ƒ(Rs^) values
can also be determined. If the maximum and
minimum ƒ(Rs^) values fall within the allowable
Table 7 - CO concentration ranges vs. alarm times
as specified by performance standard
10
C(min) C(max)
calibration point
1
ranges of the standard (Table 7), then sensors
calibrated at one CO␣ concentration could satisfy the
requirements of the performance standards. Table 8
shows maximum and minimum CO␣ concentrations
for each sensor grade compared to the range of CO
concentrations permitted by performance standards.
0.1
10
max
center
min
100
1000
4-3 Conclusion
CO Concentration (ppm)
As Table 8 illustrates, properly calibrated TGS2442
sensors can satisfy the requirements of current
Figure 12 - Variation of alarm concentrations in β grades
(Ro = Rs at 100ppm CO, 25˚C/40%RH)
Test Point
β Grade
A
B
C
D
E
F
Standard
Requirement
65ppm
60.6-69.0
60.6-69.0
60.6-69.0
60.5-69.0
60.4-69.1
60.3-69.1
48 ~ 95
CO Concentration Range (ppm)
100ppm
200ppm
300ppm
100
181-224
257-358
100
182-224
257-359
100
182-224
258-359
100
182-225
257-360
100
181-225
257-362
100
181-225
256-365
75 ~ 145
145 ~ 270
210 ~ 400
400ppm
329-500
330-501
330-502
330-504
329-507
329-511
260 ~ 520
Table 8 - TGS2442 alarm concentrations vs. performance standard requirements
Revised 04/01
9