Figure 8-5. Fault 3, Reversed Thermocouple - Emerson Rosemount Analytical Oxymitter 4000 Instruction Manual

Hazardous Area Oxymitter 4000
DIAGNOSTIC
ALARMS
CALIBRATION RECOMMENDED
TEST
POINTS
INC INC
HIGH LOW
GAS GAS
DEC DEC
KEYPAD
Alarms
O2 T/C Reversed
LOI

Figure 8-5. Fault 3, Reversed Thermocouple

Rosemount Analytical Inc. A Division of Emerson Process Management
HEATER T/C
HEATER
SW2
O2 CELL
CALIBRATION
J1
O2 CELL mV +
TP1
O2 CELL mv -
TP2
HEATER T/C +
TP3
HEATER T/C -
TP4
CAL
TEST GAS +
TP5
PROCESS -
TP6
% O2
37260021
Instruction Manual
c. Fault 3, Reversed Thermocouple Wiring
or Faulty PC Board
Figure 8-5 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 3 is
detected, the HEATER T/C LED flashes
three times, pauses for three seconds, and
repeats.
1. Using a multimeter, measure the volt-
age from TP3+ to TP4-. If the reading
is negative, the thermocouple wiring is
reversed.
2. Check red and yellow wires in the J1
connector for the proper placement.
3. If the wiring is correct, the fault is in
the PC board. See paragraph 9-4c,
Electronic Assembly Replacement.
LOI. When Fault 3 is detected, the LOI
displays the "O2 T/C Reversed" 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
3 shown for the membrane keypad.
IB-106-340C Rev. 4.1
July 2004
Troubleshooting 8-7
8