Section 4
4-12
Calibration
●
Set FCT 59 (CO
2
reference) to 300.
2.
Set the CO
2
span.
●
Flow CO
2
-free air through the chopper housing.
●
Flow 300 ppm span gas through the reference side of the analyzer.
●
Flow 500 ppm span gas through the sample side of the analyzer.
●
Send remote command *081,0,1,500 to set the span.
The procedure for setting the H
2
O zero and span is identical to the above
steps, with the exception that the air must be completely dry to set the zero,
and the span is set using an airstream containing a known water vapor
concentration, as can be provided by the LI-610 Portable Dewpoint
Generator, for example.
4.7 Using the LI-670 Flow Control Unit
The LI-670 Flow Control Unit can be a valuable accessory for operating and
calibrating your LI-6262. The following discussion describes how you can
calibrate your LI-6262 using the LI-670 and a single span gas.
Absolute and Differential Mode Calibration with One Span Gas.
Absolute mode. Set zero.
1.
Connect the LI-6262
Sample In
fitting to the LI-670
Sample Out
fitting,
and the LI-6262
Reference
In
fitting to the LI-670
Reference
Out
fitting.
2.
Enter the station barometric pressure into the LI-6262 at FCT 77.
Alternatively, you can use the 6262-03 Pressure Transducer, or an
external sensor to input the barometric pressure.
3.
Connect a span tank containing air (
not nitrogen
) with a known H
2
O or
CO
2
mole fraction to the LI-670
Sample In
and
Reference In
fittings,
and turn both the reference and sample
CO2/H2O Scrub
switches ON.
Use tank pressure to provide flow at a nominal rate near that used during
measurements. Final flow rate adjustments can be made with the
LI-670
SAMPLE
and
REFERENCE
vents.
4
.
When the reading is steady, adjust the zero potentiometer on the LI-6262
until the display reads zero.
