Figure 8-3. Fault 1, Open Thermocouple - Emerson Oxymitter 4000 Instruction Manual

Oxymitter 4000
DIAGNOSTIC
ALARMS
CALIBRATION RECOMMENDED
TEST
POINTS
INC INC
HIGH LOW
GAS GAS
DEC DEC
KEYPAD
Alarms
O2 T/C Open

Figure 8-3. Fault 1, Open Thermocouple

Rosemount Analytical Inc. A Division of Emerson Process Management
HEATER T/C
HEATER
SW2
O2 CELL
CALIBRATION
J1
O2 CELL mV +
TP1
O2 CELL mv -
TP2
HEATER T/C +
TP3
HEATER T/C -
TP4
CAL
TEST GAS + TP5
PROCESS -
TP6
% O2
LOI
37260019
a. Fault 1, Open Thermocouple
Figure 8-3 shows 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,
below the membrane keypad or the LOI
module.
Membrane Keypad. When Fault 1 is de-
tected, the HEATER T/C LED flashes once,
pauses for three seconds, and repeats.
1. Check connector J1. Ensure the con-
nector is properly seated.
2. Using a multimeter, measure TP3+ to
TP4-. If the reading is 1.2 VDC ±0.1
VDC, the thermocouple is open.
3. Remove power. Disconnect J1. Meas-
ure continuity across the red and yel-
low thermocouple leads.
4. The measurement should read ap-
proximately 1 ohm.
5. If the thermocouple is open, see para-
graph 9-4h, Heater Strut Replacement.
LOI. When Fault 1 is detected, the LOI dis-
plays the "O2 T/C Open" 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
5 shown for the membrane keypad.
Instruction Manual
IB-106-340 Rev. 3.0
December 2003
Troubleshooting 8-5