System Setup and Operation
CIRAS-2 Operator's Manual Version 2.04
- 55 -
There are 4 analog output voltages in use corresponding to the absolute and differential CO
2
and H
2
O
concentrations. The full range is 0-5 V with 8 bit (0-4% of FSD) resolution. To optimize the outputs, it is
possible to set the corresponding concentration ranges.
CO
2
Analog Outputs
Low
0 - 2,000 ppm
High
0 - 2,000 ppm
Difference
-25 - 999 ppm
H
2
O Analog Outputs
Low
0 - 75 mb
High
0 - 75 mb
Difference
-5 - 75 mb
For differential values (both CO
2
and H
2
O), an output of 2.5V corresponds to a 0 differential. Output
values below 2.5V correspond to negative differentials (-) and values above 2.5V correspond to positive
differentials (+).
Examples of Analog Outputs
Example 1.
If:
CO
2
Reference = 356 ppm
Low CO
2
= 0
High CO
2
= 2000
Then:
CO
2
Reference Voltage Output = 356/2000 x 5.0V =
0.89 V
.
Example 2.
If:
CO
2
Reference = 356 ppm
Low CO
2
= 300
High CO
2
= 400
Then:
CO
2
Reference Voltage Output = ((356-300)/(400-300)) x 5.0V =
2.8 V.
