ABB NGC8206, Руководство пользователя

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Page 2–18 2101510 Rev. AG
2.4.1 Power Supply
The power supply for the NGC should have an isolated output (the negative side
of the 12 VDC output should not be electrically connected to chassis or earth
ground). In many instances, the power supply is in conjunction with a radio. If the
radio is connected to the NGC8206 via RS232/485/422, the communications
should share the power ground. The communication shield should only be
connected at the NGC end. The other end should be left to float (left
unconnected).
2.4.2 Sample Probe
If the sample probe is mounted to a section of pipe where cathodic currents may
exist, put isolators in the sample tubing between the sample probe and the NGC.
Any time that the sample probe is on a section of pipe other than the one where
the NGC is directly mounted, tubing isolators should be employed. It is very
important that probe ground and the NGC ground be at the same potential. If this
cannot be insured, tubing isolators must be used.
2.4.3 Other Considerations
If other devices are to be powered from the same isolated power supply that is
powering the NGC, be careful to avoid any ground loops. The various devices
should be connected in a star configuration. It is also important that any additional
powered devices be able to handle a fairly wide range of input voltages, as the
NGC’s heater will draw about 4 amps (if the auxiliary heater is installed, it might be
as much as 8 amps). This load (4-8 amps) being drawn across any considerable
length of cable can result in a substantial voltage drop (refer to
Table 2–4 12 VDC
Battery Power Supply System Maximum Cable Lengths ). The resulting lower
input voltage to the additional device could affect its operation. Input voltage
excursions fluctuate with the toggling of the NGC’s heater(s). The heater(s) are
turning on and off in an effort to maintain a very constant internal temperature for
the NGC’s GC module.
In an office environment, insure that a good earth ground is established to the
NGC8206. In an office situation, it is easy to not have the NGC well grounded.
Often the third pin (ground) on the power cable is missing or has been removed.
Improper grounding can lead to erratic behavior. Be sure that the unit is properly
grounded. If the unit is not properly grounded, the user could have as much as 60
VAC (half line voltage) on the case of the equipment due to capacitive coupling
within the power supply.
2.5 Calibration/Validation Stream
On the NGC feed-through assembly, one or two of the sample streams may be
used for a calibration gas input. It is recommend that a metal diaphragm regulator
is set to 15
±
2 psig input. The recommended calibration gas component
concentrations for use with Auto Peak Find may be found in Table 2–3 .
Table 2–3 Calibration Gas Blend Recommended Components
Component
Name
Abbreviation Mol % Component
Name
Abbreviation Mol %
Nitrogen
N
2
2.500 Normal Butane
NC
4
0.300
Methane
C
1
89.570 Neo Pentane
Neo C
5
0.100
Carbon Dioxide
CO
2
1.000 Iso Pentane
IC
5
0.100
Ethane
C
2
5.000
Normal
Pentane
NC
5
0.100