Fuji Electric ZSS-8 Series Instruction Manual page 100

6.11.2 Concentration of the gas which is fed to the check cell
and gas concentration fluctuation
Based on the Lambert-Beer Law, absorption intensity is proportional to gas concentration and the length
where the gas exists (optical path lengths or stack length).
Since the check cell length is 0.25m, the gas concentration to be fed is calculated from the following equa-
tion.
Required gas cylinder concentration
= (Measuring range - Measured gas concentration inside the stack (should be stabilized)) × 4
For example, when the measurement range is from 0 to 50 ppm, and the gas concentration inside the stack is
10 ppm,
Required gas cylinder concentration = (50 - 10) × 4
= 160ppm
Feeding the gas of 160ppm to the check cell is similar to feeding the gas at the span point.
Deviation of the span point can be checked by studying difference between the concentration output at this
time and 50ppm.
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INZ-TN8ZSS-E