LI-COR LI-7500, Инструкция по эксплуатации

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Section 4
Calibration 4-9
Insert the top of the fixture first, and slide the bottom into place. It is very important that
the fixture is centered between the windows covering the source and detector modules. It
can be helpful to click on the Diagnostics tab in the 7500-50 software, and view the AGC
value while centering the fixture; if the AGC value increases when the fixture is in place,
it indicates that one or both of the windows are partially or totally obscured. Move the
fixture back and forth until the AGC value reads the same value as before the fixture was
inserted. The fixture is very easy to center; if it looks centered, it probably is.
NOTE: The three ports are entirely interchangeable.
3. Click on the Calibration tab, and verify that temperature and pressure are working OK.
(If you are using an alternate source for temperature and pressure, click on the Inputs tab
and set that up).
IMPORTANT NOTE: Always zero the instrument before spanning (don’t span,
then zero).
4. Flow CO
2
-free air through the calibration fixture at a rate of about 0.5 to 1.0 LPM.
Attach the zero gas to the calibration fixture at one of the ports shown in Figure 4-1.
Zero CO
2
5. Observe the CO
2
concentration and wait for it to stabilize (typically 1 minute). Also,
note the present value of Z
co
(Figure 4-2).