Emerson 4000 Alarms, O2 Temp Low, LOI, LOI, KEYPAD, Membrane Keypad, h. Fault 8, Low Heater Temp, Figure 8-10.Fault 8, Low Heater Temp

Instruction Manual

IB-106-340 Rev. 3.0

December 2003

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

CALIBRATION RECOMMENDED

Oxymitter 4000

h. Fault 8, Low Heater Temp

Figure 8-10shows the electronic assembly

for an Oxymitter 4000 with a membrane

keypad (upper view) and an Oxymitter 4000

with an LOI (lower view).

Membrane Keypad. When Fault 8 is de-

tected, the HEATER LED flashes four times,

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

pauses for three seconds, and repeats.
1.	The low heater temperature alarm is
	active when the thermocouple reading
	has dropped below 28.6 mV.
2.	If the thermocouple reading continues
	to ramp downward for one minute and
	does not return to the temperature set
	point of approximately 29.3 mV, then
	an Open Heater fault will be displayed.
3.	Power down the electronics. Remove

KEYPAD

Alarms

O2 Temp Low

LOI 37260026

Figure 8-10. Fault 8, Low Heater Temp

the electronic assembly per paragraph

9-4d,Electronic Assembly Replace-

ment. Using a multimeter, measure

across the heater connector, J8.

4. If the heater is good, the reading will be

approximately 70 ohms. If the heater is

open, see paragraph 9-4h,Heater Strut

Replacement.

LOI. When Fault 8 is detected, the LOI displays the “O2 Temp Low” message. Refer to the comments and procedures in paragraphs 1 through 4 above.

8-12 Troubleshooting Rosemount Analytical Inc. A Division of Emerson Process Management