XNX Universal Transmitter
Section 3 - Calibration
112
1. Obtain the star rating for both the test gas and the gas to be
detected from the Gas Star Ratings table on the previous page.
2. Set the gas selection to the star rating which is the same star
rating of the gas being detected.
3. These values may then be used in the following table to obtain
the required meter setting when a 50% LEL test gas is applied
to the detector.
Test Gas Meter Settings
1
Star Rating of
Calibration Gas
Star Rating of Gas to be Detected
8* 7* 6* 5* 4* 3* 2* 1*
8* 50 62 76 95 - - -
7* 40 50 61 76 95 - -
6* 33 41 50 62 78 95 -
5* 26 33 40 50 63 79 95 -
4* - 26 32 40 50 63 80 95
3* - - 26 32 40 50 64 81
2* - - - 25 31 39 50 64
1* - - - - 25 31 39 50
1
Use these settings only with 50% LEL calibration gas concentration.
4. If a sensor is to be used to detect a gas other than that for which
it was calibrated, the required correction factor can be obtained
from the following multiplier factors table. Multiply the meter
reading by this number to obtain the true gas concentration.
Multiplier Factors
Sensor
calibrated
to detect
Sensor used to detect
8* 7* 6* 5* 4* 3* 2* 1*
8* 1.00 1.24 1.52 1.89 2.37 2.98 3.78 4.83
7* 0.81 1.00 1.23 1.53 1.92 2.40 3.05 3.90
6* 0.66 0.81 1.00 1.24 1.56 1.96 2.49 3.17
5* 0.53 0.66 0.80 1.00 1.25 1.58 2.00 2.55
4* 0.42 0.52 0.64 0.80 1.00 1.26 1.60 2.03
3* 0.34 0.42 0.51 0.64 0.80 1.00 1.27 1.62
2* 0.26 0.33 0.40 0.50 0.63 0.79 1.00 1.28
1* 0.21 0.26 0.32 0.39 0.49 0.62 0.78 1.00
Since combustible sensors require oxygen for correct operation,
use a mixture of gas in air for calibration. Assuming average sensor
performance, the sensitivity information in these tables is normally
accurate to ±20%.
Example:
If the 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 the rst table:
Butane 4* and Methane 6*.
2. Check the meter settings for 50% LEL calibration gas in the second
table: 78.
3. Set the meter to 78% to give an accurate reading for butane using
50% LEL with methane as the calibration gas.
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