Emerson Process Management OXYMITTER 4000 - Manual (Page 101)

Instruction Manual
IB-106-340C Rev. 4.1
July 2004
Rosemount Analytical Inc. A Division of Emerson Process Management Troubleshooting 8-5
Hazardous Area Oxymitter 4000
Alarms
O2 T/C Open
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
37260019
Figure 8-3. Fault 1, Open Thermocouple
a. Fault 1, Open Thermocouple
Figure 8-3 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). 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
detected, 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 the volt-
age from TP3+ to TP4-. If the reading
is 1.2 VDC ±0.1 VDC, the thermocou-
ple is open.
3. Remove power. Disconnect J1. Meas-
ure the resistance across the red and
yellow thermocouple leads. The resis-
tance should be approximately 1 ohm.
4. If the thermocouple is open, see para-
graph 9-4g, Heater Strut Replacement.
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.
8