Section 4
4-26
Calibration
7.
Make sure that the sensor housing cable is connected to the console
(the cable from the LI-6200 console to the LI-6250 IRGA need not
be connected), and turn on the console.
Calibration: Setting
the Zero
1.
Set the LI-610 flow rate to approximately 0.2 to 0.3 liters per
minute. This low flow rate minimizes flow-related pressurization
within the LI-610 condenser. To check for condenser pressure
changes:
•
Turn off the flow and open the condenser fill/drain tube port. Note
the location of the fill/drain tube water meniscus.
•
Turn on the flow, regulate the flow to the recommended level, and
measure the change in meniscus height.
•
Calculate the flow-dependent condenser pressure as
∆
P = 0.0979
kPa cm
-1
×
water column height (in cm). This pressure factor will
be used later.
2.
For the LI-6200, the humidity lookup table (FCT 47) should match
the values given on the factory calibration sheet. The multiplier
value (FCT C7) should also read 0.024414. For the LI-6000, set the
system parameters for use with a desiccant as follows:
WINT = 0
W SLP = 0
FLOW = 0
RH IN = 0
CORR RH = Y
3.
The LI-610 should be generating a dew point of 0.05 °C. The air
stream water vapor pressure will be about 0.61 kPa. Remove the
remaining water vapor from the air by connecting a tube of fresh
anhydrous Mg(ClO
4
)
2
between the LI-610 and the sensor housing.
Alternatively, one could use a tank of compressed air as the source of
dry air; however, it may still be desirable to use a desiccant between
the tank and the sensor housing, especially if the tank pressure is low.
