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Model LXT-230 Instruction Manual / 19
8.0 TROUBLESHOOTING GUIDE
Symptom
Possible Causes
Suggested Actions
No power to the instrument.
Check power supply to be
sure the correct voltage is
being supplied to the
transmitter. (13.5 to 50
VDC)
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.
The slope calibration is mis-
calibrated. Typically the
transmitter is calibrated with
no slope (0 mV/pH).
Check buffers to make sure
they are the correct values.
Use the Back-to-Factory
calibration feature on the
Electrode Span Menu, then
perform a buffer calibration.
Check the electrode and
sensor for proper operation.
The pH fluctuates from
minimum scale to full-scale,
or the pH is locked at high or
low scale.
Wrong temperature
correction has been
calibrated in the temperature
trim.
Examine the temperature
and the Temperature
Calibration Menu. Adjust trim
as required.
The pH or ORP reading short
spans.
The transmitter may have
been mis-calibrated.
Check buffers to make sure
they are the correct values.
Use the Back-to-Factory
calibration feature on the