Pfaudler-werke Ag

Rudolf Ehret

Gerhard Hoyer

A capacitive probe for measuring fluid level has two electrodes, each of which forms a capacitor with a supporting conductive body. The first electrode is a vertical band which will yield a capacitive value dependent upon the dielectric constant, conductivity, as well as level of the fluid. The bulk of the second electrode is arranged at the lower end of the supporting body totally immersed in the liquid, and will yield a capacitance based on the dielectric constant and conductivity of the liquid, but substantially not the level of the liquid. A value indicating the liquid level independent of dielectric constant and conductivity may be obtained from the two capacitive values of the electrodes.

Compensated probe for capacitive level measurement

A tantalum electrode is provided on a probe dipping into the electrically conducting contents of a reaction vessel of which the steel shell is protected by an enamel layer pierced by one or more protective tantalum plugs and an alternating voltage is applied between the tantalum electrode and the metallic shell of the reaction vessel. Both the electrode and the plug or plugs are provided with a passivating layer by the resulting alternating current and when these layers are formed the current stops except that it continues or starts again when there is a defect in the enamel layer. Very small currents can be used since the a-c component can be filtered and amplified for reliable detection.

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Schwetzingen, Germany

Rudolf Ehret