Emerson 4000 Alarms O2 T/C Reversed, Fault 3, Reversed Thermocouple Wiring or, Faulty PC Board

Oxymitter 4000

	HEATER T/C
DIAGNOSTIC	HEATER	SW2
ALARMS	O2 CELL	ON
	CALIBRATION

CALIBRATION RECOMMENDED

Instruction Manual

IB-106-340 Rev. 3.0

December 2003

c. Fault 3, Reversed Thermocouple Wiring or

Faulty PC Board

Figure 8-5shows the electronic assembly

for an Oxymitter 4000 with a membrane

keypad (upper view) and an Oxymitter 4000

with an LOI (lower view). The upper view

also shows J1 and test points TP1 through

TP6, located on the microprocessor board,

TEST

POINTS

INC INC

HIGH LOW

GAS GAS

DEC DEC

O2 CELL mV +

O2 CELL mv - HEATER T/C + HEATER T/C -

CAL

TEST GAS + PROCESS - % O2

TP1	J1
TP2
TP3
TP4	RED YEL GRN ORG

TP5

TP6

below the membrane keypad or the LOI

module.

Membrane Keypad. When Fault 3 is de-

tected, the HEATER T/C LED flashes three

times, pauses for three seconds, and re-

peats.

1. Using a multimeter, measure TP3+ to

TP4-.

2. If the reading is negative, the thermo-

couple wiring is reversed.

KEYPAD

Alarms

O2 T/C Reversed

LOI 37260021

Figure 8-5. Fault 3, Reversed Thermocouple

3.	Check red and yellow wires in the J1
	connector for the proper placement.
4.	If the wiring is correct, the fault is in the
	PC board. See paragraph 9-4d,Elec-
	tronic Assembly Replacement.

LOI. When Fault 3 is detected, the LOI dis- plays the “O2 T/C Reversed” message.

1.Remove power. Unscrew and remove the LOI module from the electronic as- sembly.

2.Reconnect power to the Oxymitter 4000.

3.Perform the diagnostic steps 1 through 4 shown for the membrane keypad.

Rosemount Analytical Inc. A Division of Emerson Process Management Troubleshooting 8-7