Figure 8-4. Fault 2, Shorted Thermocouple - Emerson Oxymitter 4000 Instruction Manual

Instruction Manual
IB-106-340 Rev. 3.0
December 2003
DIAGNOSTIC
ALARMS
CALIBRATION RECOMMENDED
TEST
POINTS
INC INC
HIGH LOW
GAS GAS
DEC DEC
KEYPAD
Alarms
O2 T/C Shorted

Figure 8-4. Fault 2, Shorted Thermocouple

8-6 Troubleshooting
HEATER T/C
HEATER
SW2
O2 CELL
CALIBRATION
O2 CELL mV +
TP1
O2 CELL mv -
TP2
HEATER T/C +
TP3
HEATER T/C -
TP4
CAL
TEST GAS +
TP5
PROCESS -
TP6
% O2
LOI
37260020
b. Fault 2, Shorted Thermocouple
Figure 8-4 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.
J1
Membrane Keypad. When Fault 2 is de-
tected, the HEATER T/C LED flashes twice,
pauses for three seconds, and repeats.
1. Using a multimeter, measure across
2. If the reading is 0 ±0.5 mV, then a
3. Remove power and disconnect J1.
4. Measure from TP3+ to TP4-. The
5. If so, the short is not on the PC board.
LOI. When Fault 2 is detected, the LOI dis-
plays the "O2 T/C Shorted" message.
1. Remove power. Unscrew and remove
2. Reconnect power to the Oxymitter
3. Perform the diagnostic steps 1 through
Rosemount Analytical Inc.
Oxymitter 4000
TP3+ and TP4-.
shorted thermocouple is likely.
reading should be approximately 20K
ohms.
The thermocouple wiring or the ther-
mocouple is shorted. See paragraph 9-
4h, Heater Strut Replacement.
the LOI module from the electronic as-
sembly.
4000.
5 shown for the membrane keypad.
A Division of Emerson Process Management