Abstract: A level measuring probe in which all potential leakage paths are closed by concentrically shrinking the outmost diametrical surface of the probe by some mechanical means such as a crimper or rotary swager to provide sufficient force to substantially uniformly deform the ground, guard, and active elements and insulators around the circumference of the probe such that multiple seals are created. A circumferential notch is preferably provided in the active probe element at the point of the crimping or swaging to provide "blowout protection" whereby the active probe electrode is held in place when used in a high pressure vessel. A pressure seal between the electrodes and insulation material is also maintained by using an elastomeric insulator which returns to its original shape after heating or a thin electrode which "gives" a little when the insulator expands radially during heating. The arrangement of the invention thus eliminates the need for costly machined parts and bushings to provide pressure seals.

Abstract: An improved system for generating a signal representative of the level of a material having a dielectric constant within a vessel is disclosed. The system features use of a first probe for generating a signal indicative of the dielectric constant of the material which is divided into a signal varying with the level of the material whereby a compensated level signal irrespective of the actual dielectric constant is measured. In a preferred embodiment, a single integrator is used to perform the division operation whereby inaccuracies due to component variation including long-term drift are eliminated. The instrument is disclosed as functioning in a two-wire instrument system having low power requirements, permitting use of conventional signal limits.