GE CGA 351, Руководство пользователя

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December 2004
4-32 Setup and Calibration
Regulating the Calibration
Gas Flow Rate
A temporary connection may be made for calibration purposes.
However, if a permanent connection is preferred, it should be as short
as possible with an isolation valve right at the calibration gas inlet on
the analyzer. See the typical sample system in Figure 1-3 on page 1-3
for an acceptable arrangement.
Each CGA 351 is tagged with its optimum calibration gas flow rate,
based on the testing performed during its factory calibration.
Typically, this value will be 1,000 ± 150 cc/min (2.1 ± 0.3 SCFH).
To set up for calibration complete the following steps:
1.
Begin the flow of calibration gas to the inlet port of the analyzer,
at atmospheric pressure.
2.
Using the flowmeter and needle valve supplied with the analyzer,
set the calibration gas flow rate to the tagged value.
3.
Set the digital display to show the oxygen concentration in ppm
(see “Configuring the Digital Display” on page 3-3). At the
standard operating temperature of 700°C, an oxygen level of 5
ppm corresponds to a raw sensor output of 223.108 mV.
Note:
Air calibration at 20.9% O
2
/ 0.0 mV is performed during the
factory setup. Field recalibration of this zero mV point is
seldom required.
Note:
For other temperature and/or oxygen values see Appendix A,
The Nernst Equation , for the expected mV output reading.
If the analyzer does not respond correctly at the tagged calibration gas
flow rate (i.e. the oxygen concentration reading is more than 5% in
error), the problem is probably due to improper siting of the unit.
Contact the factory for assistance.
Caution!
Make sure the calibration gas flow rate does not exceed
1,200 cc/min (2.5 SCFH). Higher flow rates may cool the
oxygen sensor below the normal operating temperature
and affect the accuracy of measurements or even cause
damage to the oxygen sensor.
The oxygen concentration reading in ppm should correspond to the
certified oxygen content of the calibration gas ±5%. If the correct
ppm reading is not obtained with the calibration gas, proceed to the
next section to adjust the calibration setting.
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