VEGA Capacitive electrodes EK Profibus PA - Manual (Page 18)

18 Capacitive electrodes EK - Profibus PA
Cable electrod in solids
Mounting
Fixing
weight
Continuous electrodes
L
Non-conductive vessel
In non-conductive vessels, e.g. plastic tanks,
the second pole of the capacitor must be
provided separately, e.g. in the form of a
concentric tube.
When using a standard instrument, a suitable
grounding surface is necessary. Provide
therefore the largest possible grounding
surface, e.g. wire braiding laminated into the
vessel wall or metal foil glued to the vessel.
Connect the grounding surface to the ground
terminal on the housing.
Rod electrode
Mount the rod electrode such that the
electrode protrudes into the vessel. When
mounting in a tube or a socket, material
buildup that deters the measurement can
form. This is particularly the case with
viscous or adhesive mediums.
Cable electrode in solids
Depending on the type of solid, the filling
method and its location, the cable electrode
may "float" inspite of the gravity weight. The
electrode (cable) is pushed by the solid
against the vessel wall or to the surface, thus
causing incorrect measured values. This
should be avoided during continuous
measurement. If this happens, use a fixing
insulator to secure the cable electrode.
When securing the cable electrode, avoid
high tensile forces. An appropriate fixing
spring which prevents cable overload can be
found in our price list.
Lateral mounting
With measuring probes that deliver
continuous measured values, the electrode
must be installed vertically. If installation from
the top is not possible, the electrodes can
also be mounted laterally.
Under accessories in our price list, you can
find a screening tube and a closing cone or
an angled rod electrode with which the
instrument can also be laterally mounted.
Determine the screening tube length (L) that
will not allow product bridges to form
between cable and vessel wall, and that will
not allow the electrode cable to touch the
vessel wall through product movements. Use
a fixing weight or a fixing insulator.