Emerson Process Management OXYMITTER 4000 - Manual (Page 108)

Instruction Manual
IB-106-340C Rev. 4.1
July 2004
8-12 Troubleshooting Rosemount Analytical Inc. A Division of Emerson Process Management
Hazardous Area Oxymitter 4000
LOI
KEYPAD
DIAGNOSTIC
ALARMS
TEST
POINTS
HEATER T/C
HEATER
O2 CELL
CALIBRATION
CALIBRATION RECOMMENDED
O2 CELL mV +
O2 CELL mv -
HEATER T/C +
HEATER T/C -
INC INC
DEC DEC
HIGH
GAS
LOW
GAS
CAL
TEST GAS +
PROCESS -
% O2
SW2
TP1
J1
TP2
TP3
RED YEL GRN ORG
TP4
TP5
TP6
ON
37260026
Alarms
O2 Temp Low
Figure 8-10. Fault 8, Low Heater Temp
h. Fault 8, Low Heater Temp
Figure 8-10 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).
Membrane Keypad. When Fault 8 is
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.
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.