LI-COR LI-870, Инструкция по использованию

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Section 4. Maintenance
concentration measurements more than lower ones. The recommended order of
operation for user calibration is
1 Set the H
2
O zero.
2 Set the CO
2
zero.
3 Set the H
2
O span.
4
Set the CO
2
span.
For user calibration, additional tubing (part number 222-01824) and quick con-
nects (part numbers 300-07124 (male) and 300-07125 (female)) are included with
your spares kit.
Setting the H
2
O zero and spans
The water vapor span can be set with a dew point generator such as the LI-610. The
procedure is the same as setting the CO
2
zero and spans, only this uses known con-
centrations of water vapor rather than CO
2
.
Caution: Setting the zero and span incorrectly for either CO
2
or H
2
O will
adversely impact the performance of your instrument. If you do not have the
proper equipment to span the analyzer, it is best to leave it alone.
Setting the CO
2
zero
Always perform the zero first. To set the zero, you'll need either a tank of dry air
that is free of CO
2
or a CO
2
scrubbing chemical such as wet soda lime and a desic-
cant such as Drierite.
1 Plumb the zero-gas tank or scrubber to the air inlet.
Be sure to use an air filter to prevent contaminants from entering the optical path.
l
If using tank air, the pressure of the tank is sufficient to flow the gas through
the analyzer. Allow at least 0.75 liters per minute to flow through the cell (no
more than 1.0 lpm).
l
If using a scrubbing chemical, use a pump to draw air through the analyzer.
2 Install a 10 to 20 cm length of tubing to the air outlet.
This vent prevents ambient air from diffusing upstream into the optical cell.
4-6 Using the LI-870 CO₂/H₂O Analyzer