Fault 3, Reversed Thermocouple Wiring Or Faulty Pc Board - Emerson Rosemount Oxymitter 4000 Reference Manual

Rosemount Oxymitter 4000
Figure 8-5. Fault 3, Reversed Thermocouple

Fault 3, Reversed Thermocouple Wiring or Faulty PC Board

104
Hazardous Area Oxymitter 4000
Figure 8-5. Fault 3, Reversed Thermocouple
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 voltage 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 "Electronic Assembly
Replacement" in Section 9: Maintenance and Service.
8-9
July 2018
Fault 3, Reversed Thermoco
Faulty PC Board
Figure 8-5 shows the electronic a
Hazardous Area Oxymitter 4000 w
keypad (upper view) and a
Hazardous Area Oxymitter 4000 w
view). The upper view also shows
TP1 through TP6, located on the
board, below the membrane keyp
module.
Membrane Keypad
When Fault 3 is detected, the HE
flashes three times, pauses for th
repeats.
1. Using a multimeter, measur
TP3+ to TP4-. If the reading
thermocouple wiring is
2. Check red and yellow wires
connector for the proper pla
3. If the wiring is correct, the fa
board. See "Electronic Asse
Replacement" in Section 9:
Service.
LOI
When Fault 3 is detected, the LO
T/C Reversed" message.
1. Remove power. Unscrew and r
module from the electronic as
2. Reconnect power to the Oxym
3. Perform the diagnostic steps
shown for the membrane key
Troubleshooting
Inst
IM-
re