Maintenance
LXT-280
Teledyne Analytical Instruments
38
Table 6-1: Troubleshooting
SYMPTOM
POSSIBLE CAUSES
SUGGESTED
ACTION
No power to the
instrument.
Check power supply to be
sure the correct voltage is
being supplied to the
transmitter.
Check polarity of
transmitter wiring.
Contrast level is set too
low.
Set contrast level to a
higher value. Because the
contrast menu is always
the top menu, it can be
reached by pressing the
upper MENU SELECTION
key at least 12 times.
Enter the calibrate mode
and increase the value.
The LCD does not display.
Sensor or signal
conditioner has a short that
draws too much power
from the transmitter.
Check the sensor for
proper operation. To
verify, disconnect all
sensor wires and cycle
power off, then on.
Sensor not wired properly
Using the proper wiring
diagram, verify that the
sensor is properly wired to
the transmitter.
Sensor and the electrode
are not properly
submerged in the process
Verify that the sensor
housing and the electrode
are in contact with the
process.
Electrode cartridge is not
fully engaged in the sensor
body
Check electrode cartridge
to see that it is fully
engaged in sensor body
Erratic dissolved oxygen
readings or the sensor is
not responsive to oxygen
changes
Air bubble is trapped in
front of the electrode.
Remove the electrode
from the sensor body and
shake air bubble away
from the membrane.
Check the sensor position
with respect to horizontal.
Make sure air is not
trapped in the guard.
