Emerson Process Management IM-106-340 Fault 1, Open Thermocouple, Membrane Keypad

Instruction Manual

IM-106-340, Rev. 4.0

May 2006

Figure 8-3. Fault 1, Open Thermocouple

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

CALIBRATION RECOMMENDED

Oxymitter 4000

Fault 1, Open Thermocouple

Figure 8-3shows the electronic assembly for an Oxymitter 4000 with a membrane keypad (upper view) and a 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

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 TP2 TP3 TP4

TP5

TP6

J1 RED YEL GRN ORG

When Fault 1 is detected, the HEATER T/C LED flashes once, pauses for three seconds, and repeats.

1.	Check connector J1. Ensure the connector
	is properly seated.
2.	Using a multimeter, measure the voltage
	from TP3+ to TP4-. If the reading is 1.2
	VDC ±0.1 VDC, the thermocouple is open.
3.	Remove power. Disconnect J1. Measure
	the resistance across the red and yellow
	thermocouple leads. The resistance should
	be approximately 1 ohm.

KEYPAD

Alarms

O2 T/C Open

LOI 37260019

4. If the thermocouple is open, see "Heater

Strut Replacement" in Section 9:

Maintenance and Service.

LOI

When Fault 1 is detected, the LOI displays the "O2 T/C 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.

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