Campbell IRGASON Manuel télécharger pdf (Page 38)

IRGASON Integrated CO

O Open-Path Gas Analyzer and 3D Sonic Anemometer

8. Connect a gas tank of known CO

concentration to a pressure regulator,

then to a flow controller, and finally to the intake of the shroud.

Optimally, the concentration of span CO

should be near the concentration

of CO

being measured in the field. Begin with both the pressure regulator

and flow controller turned off. Then use the pressure regulator to slowly

increase pressure to the recommended setting for the flow controller. Next

set the flow between 0.4 and 0.6 l/min. Watch the ECMon zero-and-span

graph for the CO

measurement readings to stabilize (5 to 10 minutes).

Once stable, write down the reported CO

concentration.

Use mixtures of CO

and ambient air for the CO

span gas. The

use of reference CO

gas mixtures in pure nitrogen will lead to

errors due to a carrier gas effect on pressure-broadening of the

absorption lines since oxygen gas has a smaller line-

broadening coefficient than nitrogen.

NOTE

FIGURE 9-4. ECMon zero-and-span window

9. Remove the CO

span gas from the inlet of the shroud, and replace it with

O span gas from a dew-point generator or another standard reference.

Because water molecules can adsorb to inside of the tubing and the shroud,

it may take many minutes for the H

O concentration to stabilize. If

desired, increase the flow rate for the first several minutes to more quickly

stabilize the system before returning it to between 0.4 and 0.6 l/min to

make the H

O measurement. Write down the reported H

O concentration.

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Campbell IRGASON Manuel Page 38