Sierra Monitor Corporation 4105 - Manual (Page 18)

Instruction Manual
Model 4105 Gas Sensor Module (12/02) Page: 15
Appendix C: Combustible Gas Scaling Factors (Table 1)
Where possible, calibration gas should be the same as the gas to be detected. If this is not possible then a scaling factor
should be used to determine the “equivalent value” of the calibration gas in terms of the gas to be detected. (Note:
Concentration of calibration gas must be less than the factor number listed on Table 1).
The formula for calibration is as follows:
Display = (Cal gas) / Factor
where: Display = the span gas applied
Cal gas is the percent methane used for calibration.
Factor is a number that corresponds to the gas to be measured. (see Table 1)
Example: The application is for measurement of Propane and Methane is the calibration gas.
The factor for Propane (from Table 1) is 55.
For the example, calibration gas is Methane at 40% LEL.
Display = 40% LEL Methane / 55 = 0.73
Display = Adjust span until LCD reads 73.