Emerson Process Management OXYMITTER 4000 Alarms O2 Temp Low, Fault 8, Low Heater Temp

Instruction Manual

IB-106-340C Rev. 4.1 July 2004

Hazardous Area Oxymitter 4000

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

CALIBRATION RECOMMENDED

h. Fault 8, Low Heater Temp

Figure 8-10shows 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).

Membrane Keypad. When Fault 8 is

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

detected, the HEATER LED flashes four

times, 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.

KEYPAD

Alarms

O2 Temp Low

LOI 37260026

Figure 8-10. Fault 8, Low Heater Temp

3. Power down the electronics. Remove

the electronic assembly per paragraph

9-4c,Electronic Assembly Replace-

ment. Using a multimeter, measure the

resistance across the terminals of

heater connector, J8.

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

approximately 70 ohms. If the heater is

open, see paragraph 9-4g,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