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72 Troubleshooting
S
ection 4: Troubleshooting
6
888Xi Advanced Electronics Instruction Manual
December 2012 PN 51-6888Xi
4.2 General
Consider the following equipment conditions, features, and requirements when troubleshooting
a problem.
4.2.1 Grounding
It is essential that adequate grounding precautions are taken when installing the system.
Thoroughly check both the probe and electronics to ensure the grounding quality has not
degraded during fault finding. The system provides facilities for 100% effective grounding and
the total elimination of ground loops.
4.2.2 Electrical Noise
The 6888Xi has been designed to operate in the type of environment normally found in a boiler
room or control room. Noise suppression circuits are employed on all field terminations and
main inputs. When fault finding, evaluate the electrical noise being generated in the immediate
circuitry of a faulty system. Ensure all cable shields are connected to earth.
4.2.3 Electrostatic Discharge
Electrostatic discharge can damage the ICs used in the electronics. Before removing or handling
the circuit boards, ensure you are at ground potential.
4.3 Alarm Indications
The first indication of a problem at the O
2
measuring system usually comes from the operators
running the process. Critical alarms that render the O
2
measurement unusable will force the 4-20
mA analog output signal representing O
2
to go to a default condition, as follows:
WARNING
Install all protective equipment covers and safety ground leads after troubleshooting. Failure to install
c
overs and ground leads could result in serious injury or death.
4-20 mA Signal Alarm Level Transmitter Condition
0 mA Transmitter unpowered, or completely failed
3.5 mA Critical Alarm - transmitter reading unusable (factory default)
3.8 mA
Reading Under Range
(Example - user sets range to 2-10%. Current reading is 1.9%)
4 to 20 mA Normal Operation
20.5 mA Reading Over Range (Example - range is 0-10%. Current reading is 12%)
>21 mA
Critical Alarm - transmitter reading is unusable (user can choose this
alarm level instead of the factory default level of 3.5 to 3.6 mA)
Table 4-1 - Alarm Indications