User guide

I-E67-84-1B February,2002 14-6
visually check the following:
Sensor body
Inspect the sensor body for cracks and
distortions. If any are found, contact ABB
for alternative sensor styles and materials.
Cable and connectors
Inspect the sensor cable for cracks, cuts, or
shorts. If a junction box and/or extension
cable are used, check for moisture, oil,
corrosion, and/or particulates. All
connections must be dry, oil-free, corrosion-
free, and particulate-free. Even slight
amounts of moisture, skin oils, corrosion, and
particulates can short sensor signals due to
the high impedance of these signals. If a BNC
connector is used, check to see that it is dry
and not shorting against any metal, earth
grounds, or conduit.
Measuring electrode
Inspect the glass electrode for breaks or
cracks. If breakage is a problem, contact ABB
for alternative electrode choices or
suggestions regarding alternate sensor
mounting locations.
Inspect the measurement electrode for foulants
or scales. Many scales are not noticeable
when the sensor is wet. Using a tissue, dry
the glass electrode and hold it up to a bright
light. Scaling will appear as a whitish,
textured material on the surface of the
electrode. Films will usually have a streaky,
multi-colored appearance. Clean the electrode
if it is fouled or scaled. See Section 15,
Maintenance, for sensor cleaning procedures.
Reference junction
Inspect the reference junction (the area
between the sensor body and measuring
electrode) for heavy foulants or scaling. If
foulants or hardness scales are present,
remove foreign material using the procedures
described in Section 15, Maintenance.
When mechanically cleaning the sensor, always
use a soft bristle brush in order to avoid
damaging the insulating coating on the
solution ground (i.e., the metallic collar
around the measuring electrode if present).
This coating is only present on the outer
diameter next to the reference junction and
must be intact for the reference diagnostics
to function properly.