Oxymitter 4000

 

HEATER T/C

 

DIAGNOSTIC

HEATER

SW2

ALARMS

O2 CELL

ON

 

 

CALIBRATION

 

CALIBRATION RECOMMENDED

Instruction Manual

IB-106-340 Rev. 3.0

December 2003

a. Fault 1, Open Thermocouple

Figure 8-3shows 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

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

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.

KEYPAD

AlarmsO2 T/C Open

LOI

37260019

Figure 8-3. Fault 1, Open Thermocouple

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 displays 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.

Rosemount Analytical Inc. A Division of Emerson Process Management

Troubleshooting 8-5