United Process Controls, Inc.
Oxyfire-LT Installation/Operation Manual
19 |
P a g e
6 TROUBLESHOOTING
6.1
ITEMS REQUIRED
The following items are required to troubleshoot the Oxyfire sensor.
A digital multimeter (with DC millivolt ranges)
Blade and Phillips screwdrivers
Needle-nose pliers
Verification gas or portable oxygen analyzer
Oxygen/Temp/Millivolt Chart (See Appendix)
Sensor wiring schematic (See Appendix)
6.2
SIGNAL TROUBLESHOOTING
a.
Sensor must be in the process at normal operation and heater is in operation with sensor temperature
above 1000°F (550°C).
b.
Use a portable analyzer or verification gas to verify sensor reading. If sensor does not verify or the
verification cannot be performed, proceed to
step c
.
c.
Verify that the reference air tubing is connected to the correct port on the sensor.
d.
Verify that the verification port on the sensor is capped tightly to prevent any air in-leakage.
e.
Check sensor reference air for proper flow and pressure. Verify air is reaching sensor port by
disconnecting the supply tubing at the sensor and place the tubing in a cup of water. If you see no
bubbles or a very slow flow of bubbles, increase the reference air flow at the supply until a steady
flow of bubbles is achieved.
f.
Dry and reconnect the air tubing to the sensor port and proceed to
step g
. A higher than normal oxygen
reading may be observed if the reference air flow is low. A lower than normal reading may be
observed if the pressure and flow is too high.
g.
The sensor is supplied with a cable approximately 8 feet long. It is attached to the terminal screws
inside the terminal head of the sensor. If the cable has not been removed then follow these steps:
i.
Isolate the sensor from the rest of the system by disconnecting the sensor cable.
ii.
At the sensor cable, measure and note the cell millivolts across the (+) wire and the (-) wire.
This measurement should fluctuate. Next, measure and note the thermocouple millivolts
across the (+) wire and the (-) wire. This measurement should be fairly stable
iii.
Using the charts in the appendix, look up the temperature and oxygen. Compare the readings
to what you were seeing in the electronics. They should match. If the readings do not match,
reconnect the wires to the cable running to the electronics. Measure the same millivolt
readings at the terminals on the electronics. They should match. If not, trace all wires and
connections to see if they are crossed or connected in error. The shield wire should only be
connected at the electronics ground. If everything checks out, then disconnect the shield to see
if a ground loop or interference is involved. If everything checks out OK and the readings are
still incorrect, call Marathon Monitors Inc. for further assistance.
h.
If the factory cable has been removed:
i.
Remove the terminal cover from the sensor and verify that all connections are correct. See
Appendix.
ii.
Isolate the sensor from the rest of the system by disconnecting the cable from the terminal
connections inside the sensor terminal head. Make note of wiring connections before
disconnecting. Do not disconnect the sensor’s internal wires or damage to the sensor may
occur.
iii.
Measure and note the cell millivolts across the internal (+) wire and the (-) wire. This
measurement should fluctuate. Next, measure and note the thermocouple millivolts across the
