Emerson Process Management OXYMITTER 4000 - Manual (Page 110)

Instruction Manual
IB-106-340C Rev. 4.1
July 2004
8-14 Troubleshooting Rosemount Analytical Inc. A Division of Emerson Process Management
Hazardous Area Oxymitter 4000
Alarms
O2 Cell Open
LOI
KEYPAD
DIAGNOSTIC
ALARMS
TEST
POINTS
HEATER T/C
HEATER
O2 CELL
CALIBRATION
CALIBRATION RECOMMENDED
O2 CELL mV +
O2 CELL mv -
HEATER T/C +
HEATER T/C -
INC INC
DEC DEC
HIGH
GAS
LOW
GAS
CAL
TEST GAS +
PROCESS -
% O2
SW2
TP1
J1
TP2
TP3
RED YEL GRN ORG
TP4
TP5
TP6
ON
37260028
Figure 8-12. Fault 10, High Cell mV
j. Fault 10, High Cell mV
Figure 8-12 shows the electronic assembly
for a Hazardous Area Oxymitter 4000 with
a membrane keypad (upper view) and a
Hazardous Area Oxymitter 4000 with an
LOI (lower view). The upper view also
shows J1 and test points TP1 through TP6,
located on the microprocessor board, below
the membrane keypad or the LOI module.
Membrane Keypad. When Fault 10 is
detected, the O2 CELL flashes once,
pauses for three seconds, and repeats.
1. Using a multimeter, measure across
TP1+ to TP2-. If you measure 204 mV
to 1 volt DC, the cell reading is due to
high combustibles. This is a self-
clearing alarm, once the combustible
conditions go away. If you measure
1.2 VDC, the cell wires, either orange
or green, have become detached from
the input.
2. One possible cause is connector J1.
The orange or green wire has come
loose from the crimped connection.
3. The platinum pad could also be at fault.
The pad could have broken free from
the back of the cell.
4. Replace heater strut per paragraph
9-4g, Heater Strut Replacement. If
necessary, replace the cell and flange
assembly per paragraph 9-4h, Cell
Replacement.
LOI. When Fault 10 is detected, the LOI
displays the “O2 Cell Open” message.
1. Remove power. Unscrew and remove
the LOI module from the electronic
assembly.
2. Reconnect power to the Oxymitter
4000.
3. Perform the diagnostic steps 1 through
4 shown for the membrane keypad.