Abstract: A two-wire sensor (6) is attached to one pole of a voltage distribution source (U) by an initial connecting line (V1) in which a current-limiting resistor (R1) is positioned and is attached to the other pole by a second connecting line (V2). Parallel to the series connection consisting of the two-wire sensor (S) and the current-limiting resistor (R1) is at least one limiting diode (D1). A current regulator (SR) which is attached to the poles of the power source (U) regulates a parallel current (I) which runs parallel to the current through the two-wire sensor (D), so that there is a sum current at the poles of the power source (U) that always corresponds to the measured value delivered by the two-wire sensor (S). The regulating inputs of the current regulator (SR) are connected to the terminals of a current-sensing resistor (R2) positioned in a connecting line (V1). When a HART®-interface is used with the two-wire sensor (S) a HART®-resistor (RH) is positioned in one of the two connecting lines (V1).

Abstract: An antenna connected to a waveguide can be used for level measurements of a bulk material by measuring the reflection of microwave radiation radiated towards the surface of the bulk material. Condensate droplets forming on the antenna may produce higher modes and echoes in the microwave signal. The effect caused by droplets can be ameliorated by increasing the size of the antenna and the waveguide. To obtain a usable measurement signal, a compromise between reducing the interference from condensate droplets and optimizing the electrical characteristics has to be found. The invention is directed to a waveguide which is designed to propagate at a particular frequency only the fundamental mode, while the antenna itself is capable of supporting higher order modes. A taper which is a dimensioned so as to transmit only the fundamental mode of the microwave signal, is placed between the waveguide and the antenna.

Abstract: An antenna for a radar unit for level measurement has a dielectric rod radiator for radiating microwaves in a main radiation direction. A coupling sleeve is provided with an external thread for installation by screwing into a holder opening. The coupling sleeve contains an at least partially approximately hollow cylindrical inner part made of dielectric material that projects in the main radiation direction out of coupling sleeve. A hollow guide system includes an HF coupling device and hollow guide tube that is received in an inner part. As viewed in the main radiation direction, the rod radiator is located releasably or permanently at the forward end of the inner part.