Field of the Invention
The invention relates to an antenna for a level meter with an antenna housing, with at least one supply element and with at least one lens, wherein the lens has at least a first lens surface and a second lens surface, wherein the supply element is used for guiding coupled electromagnetic radiation and radiating electromagnetic radiation in the direction of the first lens surface, wherein, with the lens, the electromagnetic radiation received via the first lens surface can be relayed and can be emitted via the second lens surface on the process side.
Description of Related Art
The antennae being discussed here are used, for example, in level meters employing the radar principle, wherein, in addition to the antenna, the level meters comprise an electronic transmitting and evaluating unit. Electromagnetic waves are generated by the electronic transmitting and evaluating unit and led over a suitable transmission path to the antenna. The antenna itself can be implemented in various manners. For example, it can be a dielectric antenna or a horn radiator; the antenna can also be implemented as a combination of various antenna technologies. Presently, the exact type of antenna is not of importance. However, it is relevant that the antenna comprises a lens.
Often, such antennae are used in difficult measuring environments, for example, in silos or other containers that may, for example, be filled with a dusty medium. Such antennae are also used in the food industry and the pharmaceutical industry. It is possible that the lens of the antenna comes into contact with the medium. Use in difficult measurement environments leads to dust or a condensate adhering to the antenna lens and building up, thus contaminating the lens. This then interferes with the measurement signal culminating in an impossibility of use for further measurements. Cleaning the antenna or antenna lens is then necessary in order to guarantee a proper functioning of the antenna, for example, to guarantee the necessary accuracy of a level measurement.
It is known from the prior art to flush, to cool or to heat antennae so that a flushing line for a flushing medium is led through the process flange or the process tank and, sometimes quite complexly, led to the antenna. Such a flushing device is used, for example, in the radar level meters “BM 70 A” and BM 70 P” of the applicant.
In general, the antenna lens is made of a plastic, for example, PEEK (polyetheretherketone). It can be a problem in lenses known from the prior art that use under extreme conditions, such as a very high or a very low temperature or at high pressures, is afflicted with disadvantages. Operating under high pressures creates tension in the lens, which can lead to an altered transmitting characteristic of the lens or to destruction of the lens.
Due to their material, plastic lenses have a low yield strength, which sinks further at an increase in temperature. This results in that they are not durable under high pressure, thus, are not suitable for use in extreme conditions.