26
Program Mode
Change Dilution Ratio?
Attach an optional dilution fitting on the gas inlet port to dilute the gas
sample. Enter a dilution ratio (from 1 to 10) to compensate the reading
for the actual gas concentration.
Change PID Lamp Type?
This only applies to PID monitors. The PID sensor can utilize either
a 10.6 eV or an 11.7eV UV. Since each lamp type has a different
correction factor table, it is important to select the correct lamp type.
Correction Factors
VOC and LEL sensors respond to a broad range of gases and show
a different sensitivity to different gases; correction factors allow
measurement of a specific gas (the measurement gas) while using a
different gas for calibration (the calibration gas). The correction factor
(CF) for a measurement gas is defined as:
CF = Sensitivity to a Calibration Gas ÷ Sensitivity to a Measurement Gas
To convert the monitor reading of the calibration gas to the true
concentration of a measurement gas, use the following equation:
True Concentration (ppm) = CF x Monitor Reading (ppm)
The monitor has three sets of correction factors, one for the LEL and
two for the VOC (10.6 eV and 11.7 eV) Each set consists of 20 to 40
different gases. Specify the PID lamp type (e.g. 10.6 eV or 11.7 eV) to
access the proper VOC correction factor.
To set up a correction factor, first choose a calibration gas in the
Calibrate Monitor program menu and then choose a measurement
gas in the Change Sensor Configuration menu. If the calibration gas is
different from methane for LEL or isobutylene for PID, then the new CF
is calculated and the displayed value will be different from the values in
Technical Notes 106 or 156.
NOTE:
Correction factors provide an estimate of the measurement gas
concentration. For greatest accuracy, it is necessary to calibrate the
LEL or VOC sensor directly with the measurement gas.
Refer to Technical Note-106 Correction Factors and/or Technical Note-
156 LEL Correction Factors.
