Vega Capacitive electrodes EL … Bedienungsanleitung PDF herunterladen (Seite 42)

42 Capacitive electrodes EL …

Diagnosis

Contact 4 against middle pin (1)

The resistance must be 1 MΩ .

If the resistance is less, this means humidity in the housing or a failure in

the electrode isolation. A possible reason could be a not isolated

electrode which is used in conductive (humid) product.

If the resistance is higher or if the connection is interrupted, the reason is

mainly a bonding failure in the adapter plate or a defect resistor due to

strong electrostatic discharge.

In both cases the electrode must be repaired at VEGA.

Contact 4 against vessel

The connection between contact 4 and the metal vessel (not instrument

hexagon or electrode flange) should be as good as possible. Measure

with an ohmmeter (range very low) the resistance value between contact 4

and the vessel.

• Shortcircuit (0 … 3 Ω), optimum connection

• Resistance > 3 Ω

- corrosion on the mounting boss or flange

- probably the mounting boss was covered with Teflon tape or

similar

Check the connection to the vessel. If there is no connection, you can

connect a line from the earth terminal outside to the vessel.

Note that coated flanges must be in any case connected via the earth

terminal to the vessel.

Contact 7 against middle pin (1)

The resistance must be infinite (>10 MΩ).

If the resistance is less, humidity penetrated or the compensation

capacitor is defect.

Contact 3 against 4

On electrodes without screen the resistance is infinite (>10 MΩ). On EL 26

the resistance must be 1 MΩ . In case of lower values, the electrode

isolation is defect or humidity penetrated into the instrument housing.

In case of higher values, a bonding failure in the adapter place is the case

or the resistor is defect.

Contact 4 against 6

In case of older sensors and EL 29 the resistance is infinite, with new

electrodes <3 Ω. In case of values between 3 Ω and 10 MΩ there is a

defect.

When you cannot find a failure on the electrode, replace the oscillator

against a similar replacement type (if available) or send the electrode for

repair to VEGA.

If the failure does not disappear after inserting of a replacement

electronics, the adjustment on the signal conditioning instrument should be

repeated as the oscillators have certain tolerances.

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