Probe holder with spacer

#The invention relates to a probe holder for a fill level measuring device operating with the radar principle having a holder housing, having a signal conductor for guiding emitted and/or received signals and having a spacer, wherein the signal conductor is led out of the interior space of the holder housing through a wherein opening of the holder housing into the process side exterior space of the holder housing, wherein the spacer is arranged in the opening of the holder housing and keeps the signal conductor spaced from the holder housing in the opening.

#Fill level measuring devices that operate using the radar principle are used for measuring fill levels in containers such as, for example, tanks or silos. Often, so-called guided radar systems tare used here, which are based on the principle of time domain reflectometry (TDR); the probe holders mentioned in the introduction are of interest for such devices. As opposed to the so-called freely radiating radar systems, electromagnetic signals are generated here by an electronics assembly, fed into a probe and guided along the probe in the direction of the medium whose fill level is to be measured. The extension of the probe defines the measuring range of the fill level measuring device. During operation, the probe extends at least partially into the medium. The end of the probe coming into contact with the medium is usually designed as a free end, however, it can be attached to the floor of the container. Due to an existing jump in the refractive index or, respectively, the permittivity, the signals guided via the probe are at least partially reflected by the surface of the medium when entering the medium and travel back to the electronics assembly on the probe. The fill level of the medium is determined from the running time between emitting the electromagnetic signals and receiving the reflected signals. Usually, very short radio pulses are used as signals.

#The principle of time domain reflectometry is, in particular, advantageous because the properties of the medium, for example, density, conductivity and permittivity have little or no influence on measurement. The surrounding conditions, such as pressure and temperature, in the process area also do not influence the measurement results; changing surrounding conditions, like an increasing or decreasing surrounding pressure or an increasing or decreasing surrounding temperature do not affect the measuring accuracy of a TDR fill level measuring device. Measurement using the TDR principle is also suitable for determining separation layer and thus for indicating the overall fill level of the medium, on the one hand, and for indicating the height of the separation layer, on the other hand.

#FIG. 1 is a cross-sectional view of a first design of the probe holder according to the invention,

#FIG. 2 is a cross-sectional view of a second design of the probe holder according to the invention, and

#FIG. 3 is a cross-sectional view of a third design of the probe holder according to the invention.

#A probe holder 1 according to the invention for a fill level measuring device operating with the radar principle is depicted in FIG. 1. The probe holder 1 comprises a holder housing 2 and a signal conductor 3. The signal conductor 3 is led out of the interior space 5 of the holder housing 2 through a wherein opening 6 of the holder housing 2 into the wherein exterior space. The process side exterior space is not depicted in the form of a closed process area, however is illustrated by the arrow designated with P.

#The signal conductor 3 is used for guiding emitted and/or received signals, wherein an emitted signal is generated by conventional electronics that are not shown and are coupled into the signal conductor on the electronics side—indicated by an arrow designated with E. A received signal is coupled into the signal conductor 3 on the process area side and led to electronics implementing an evaluation unit. In order to guide the signals, the signal conductor 3 is formed of a metal.

#The holder housing 2 is also made of a metal. A spacer 4, which keeps the signal conductor 3 spaced from the holder housing 2, is arranged in the opening 6 so that the signal conductor 3 does not come into contact with the holder housing 2. The spacer 4 is formed of an electrical isolating material.