Vega Capacitive electrodes EL … Bedienungsanleitung PDF herunterladen (Seite 27)

Capacitive electrodes EL … 27

Mounting

Fig. 2.4 Humidity

Humidity from outside

Turn the cable entries of horizontally mounted

instruments after installation to the bottom to

avoid humidity ingress. The instrument housing

can be hence rotated by approx. 330°. For

vertically installed electrodes loop the

connection line to the electrode housing to the

bottom so that rain and condensation water

can drain off.

This is mainly valid for mounting outside, in

areas where humidity must be expected (e.g.

by cleaning processes) or on cooled or heated

vessels (see fig. 2.4).

Cable entries

When mounting outside, on cooled vessels or in

humid areas where cleaning is made e.g. with

steam or high pressure, the seal of the cable

entry is very important.

Use cable with a round cross-section area of

conductor and tighten the cable entry. The

cable entry is suitable for cable diameters of

4 mm up to 12 mm.

Two Pg-seal rings are attached to the

instrument:

- for cable diameter of 4…9mm

- for cable diameter of 5 … 12 mm.

Use the smallest possible seal ring.

Aluminium vessel

In Aluminium vessels use an electrode with

steel mounting thread. Combination Aluminium

on Aluminium should be avoided as the thread

"seizes“ and can no more be removed after

some time without damage.

Metal vessel

Note that the mechanical connection of the

electrode is electrically conductive connected

with the vessel to ensure sufficient earth.

Use conductive seals such as e.g. copper, lead

etc. Isolating measures such as covering the

thread with Teflon tape can interrupt the

necessary electrical connection. In this case

use the earth terminal on the housing to

connect the electrode to the vessel wall.

Non-conductive vessels

In non-conductive vessels, e.g. plastic tanks,

the second pole of the capacitor must be

provided separately, e.g. by a concentric tube

or the use of a double rod electrode.

When using a standard electrode, a suitable

earth plate is necessary. Hence provide a

possibly large earth plate, e.g. wire braiding

laminated into the vessel wall or metal foil

which is glued to the vessel. Connect the earth

plate with the earth 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, build-up can be

caused which can influence the measurement.

This is particularly the case with viscous or

adhesive mediums.

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