Section 2. Configuring the gas analyzer
Example 2:Computing CO
2
from a voltage output; 300 to 500 ppm range
In this example, let's configure the output range for 0 V = 300 ppm and 5 V = 500
ppm, so the full range is 200 ppm, and notably, 0 V is no longer 0 ppm.
2-6
CO2
max
is the reading that corresponds with the high voltage output (500 ppm in
this case), and CO2
min
is the reading that corresponds with the low voltage output
(300 ppm in this case). With an output voltage of 2.9, the concentration is:
2-7
Example 3: Computing CO
2
from a current output; 0 to 500 ppm range
Unlike the voltage outputs, which are 0 to 2.5 or 0 to 5 V, the current outputs are
from 4 to 20 mA. Therefore, the range is always 16 (20 - 4), and the offset is always
4. Electrical current is indicated with I. In this example, let's configure the output
range for 4 mA = 0 ppm and 20 mA = 500 ppm. The concentration is computed
from:
2-8
If the current is 16.25 mA, then
2-9
Example 4: Computing CO
2
from a current output; 300 to 500 ppm range
In this example, let's configure the output range so that 4 mA = 300 ppm and 20
mA = 500 ppm. Now, we need an offset that corresponds with the minimum CO
2
reading (300 ppm).
2-10
If the current is 16.25 mA, then
2-11
2-6 Using the LI-830 and LI-850 Gas Analyzers
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