ABB AWT420 Operating Instruction page 88

88 AW T4 2 0 | U N I V E R S A L 4 - W I R E , D U A L- I N P U T T R A N S M I T T E R | O I/A W T4 2 0 - E N R E V. B
...16 Troubleshooting
...Diagnostic messages
... pH diagnostics
NAMUR Diagnostic
icon message
S(n):
Process Temp
Out of Range
S(n):
Reference
Warning
S1:
Slope Low
S(n):
Ambient Temp
Out of Range
S(n):
Ref. Blocked
S(n):
Out of Solution
S(n):
Low Electrolyte
Cause
Solution temperature is outside the
measurement range of the sensor.
Refer to the sensor data sheet to determine
the temperature range.
The measurements taken from the reference
electrodes indicate that the reference
electrodes are becoming contaminated
(Reference Poisoning).
This is an early indication that the reference
measurement is likely to fail, at which point the
sensor has reached the end of its serviceable
life and requires replacement.
The pH sensor is reaching the end of its
serviceable life.
A pH sensor degrades over time. As this
happens the slope calculated by a calibration
procedure gradually decreases.
A Low Slope Limit is configured in Sensor Setup
– see page <?>.
If the slope calculated by a calibration
procedure is less than Low Slope Limit, the
calibration fails.
If the slope calculated by a calibration
procedure is within 20% of the Low Slope Limit,
the Low pH Slope diagnostic is activated
indicating that the sensor is reaching the end of
its serviceable life and soon requires
replacement.
The electronics in the head of the probe are
exposed to temperatures outside the
recommended operating range.
The measurement taken from the reference
electrode indicates that the reference electrode
is blocked.
This warning may also occur if the probe is not
properly immersed in solution.
Sensor readings indicate that the sensor is not
properly immersed in process solution.
The electrolyte level (in the pH sensor) is low.
Recovery action
Ensure that the solution temperature is within the sensor
measurement limits.
Check the process and reduce the effect of any potential heat sources.
If Process Temperature Out of Range is consistently active it may be
necessary to replace the sensor with an alternative with a wider, or
more appropriate temperature range. Contact local service
organization for potential solutions.
Visually inspect sensor tip for signs of damage or dirt and clean if
necessary.
Contact local service organization to order a new sensor.
1. Visually inspect sensor tip for signs of damage or dirt and clean if
necessary.
2. Check that sensor tip is fully submerged in the solution.
3. Ensure that the buffer solutions have been made up accurately and
have been correctly selected in the transmitter.
4. Repeat calibration, if Low pH Slope persists then this indicates that
the sensor is reaching the end of its serviceable life.
Move the sensor to a location where the ambient temperature within
the operating range.
If Ambient Temperature Out of Range is consistently active it may be
necessary to replace the sensor with an alternative with a wider, or
more appropriate operating range. Contact local service organization
for potential solutions.
Visually inspect sensor tip for signs of damage or dirt and clean if
necessary.
Ensure pH probe is submersed in solution.
If Reference Blocked persists, contact local service organization.
Visually inspect the sensor for signs of damage and clean the tip if
necessary.
Check that the sensor is properly immersed in the process solution.
If Out of Solution persists, contact local service organization.
If compatible, top up the electrolyte reservoir with liquid electrolyte.
Otherwise contact local service organization.