Honeywell MPD Series Operating Manual page 23

* Rating of
Calibration
4. If a sensor is to be used to detect a gas other than that for which it was
calibrated, the required correction factor may be obtained from Table 3.
The meter reading should be multiplied by this number in order to obtain
the true gas concentration.
Sensor
calibrated to
detect
8*
7*
6*
5*
4*
3*
2*
1*
NOTe
Since combustible sensors require oxygen for correct operation, a mixture
of gas in air should be used for calibration purposes. Assuming average
performance of the sensor, the sensitivity information in Tables 1 to 3 is
normally accurate to +20%.
EXAMPLE
If target gas to be detected is Butane and the calibration gas available is Methane
(50% LEL):
1. Look up the star rating for each gas in Table 1: Butane 4* and Methane 6*
2. Check the meter settings for 50% LEL calibration gas in Table 2; in this
case, 78
3. The meter should therefore be set to 78% to give an accurate reading for
Butane using 50% LEL Methane as a calibration gas.
NOTe
It is important to calibrate the sensor at the approximate alarm levels to
allow for non-linearity of the sensors at gas concentrations above 80% LEL.
MPD Operating Manual
Gas 8* 7*
8*
50 62
7*
40 50
6*
33 41
5*
26 33
4* - 26
3*
-
2*
-
1*
-
Table 2. Meter Settings
8* 7*
1.00 1.24
0.81 1.00
0.66 0.81
0.53 0.66
0.42 0.52
0.34 0.42
0.26 0.33
0.21 0.26
Table 3. Meter Multiplication Factors
* Rating of Gas to be Detected
6* 5* 4*
76 95
61 76 95
50 62 78
40 50 63
32 40 50
- 26 32 40
- - 25 31
- - - 25
Sensor Used To Detect
6* 5* 4*
1.52 1.89 2.37
1.23 1.53 1.92
1.00 1.24 1.56
0.80 1.00 1.25
0.64 0.80 1.00
0.51 0.64 0.80
0.40 0.50 0.63
0.32 0.39 0.49
3* 2* 1*
- -
-
95 -
79 95
63 80 95
50 64 81
39 50 64
31 39 50
3* 2*
2.98 3.78
2.40 3.05
1.96 2.49
1.58 2.00
1.26 1.60
1.00 1.27
0.79 1.00
0.62 0.78
-
-
-
1*
4.83
3.90
3.17
2.55
2.03
1.62
1.28
1.00
23