Impedance matched guided wave radar level gauge system

Abstract

A radar level gauge system, for determining a filling level of a product contained in a tank, the radar level gauge system comprising: a transceiver for generating, transmitting and receiving electromagnetic signals; a probe electrically connected to the transceiver at a probe-transceiver connection and arranged to extend towards and into the product contained in the tank, for guiding a transmitted signal from the transceiver towards a surface of the product, and for returning a surface echo signal resulting from reflection of the transmitted signal at the surface back towards the transceiver; an impedance matching device arranged to extend along a portion of the probe inside the tank, an extension of the impedance matching device, in a direction perpendicular to the probe, decreasing along the portion of the probe with increasing distance from the probe-transceiver connection, to thereby provide impedance matching between an impedance of the probe-transceiver connection and an impedance of the probe; and processing circuitry connected to the transceiver for determining the filling level based on the surface echo signal.

Description

TECHNICAL FIELD OF THE INVENTION [0001]The present invention relates to a radar level gauge system of the GWR (Guided Wave Radar) type for determining a filling level of a product contained in a tank.TECHNICAL BACKGROUND [0002]Radar level gauge (RLG) systems are in wide use for determining the filling level of a product contained in a tank. Radar level gauging is generally performed either by means of non-contact measurement, whereby electromagnetic signals are radiated towards the product contained in the tank, or by means of contact measurement, often referred to as guided wave radar (GWR), whereby electromagnetic signals are guided towards and into the product by a probe acting as a waveguide. The probe is generally arranged to extend vertically from the top towards the bottom of the tank. The probe may also be arranged in a measurement tube, a so-called chamber, that is connected to the outer wall of the tank and is in fluid connection with the inside of the tank.[0003]The trans...

AI Technical Summary

Benefits of technology

The present invention provides an improved radar level gauge system for determining the filling level of a product in a tank. The system includes a probe for guiding electromagnetic signals and a transceiver for transmitting and receiving the signals. An impedance matching device is used to match the impedance of the probe and the transceiver, allowing for a smooth transition of signals. The system can be used in metallic or non-metallic tanks and can provide accurate measurements even in cases where the tank has a narrow existing through-hole in the wall. The system is compact and can be easily installed in tanks.

Problems solved by technology

This may in turn make it difficult to determine the filling level when the surface of the product is close to the ceiling of the tank, and may, furthermore, reduce the maximum measurable distance (minimum measurable filling level) because of the loss of signal that occurs at the impedance transition between the feed-through and the probe.

A drawback of the impedance matching arrangements disclosed in U.S. Pat. No. 6,681,626 or U.S. Pat. No. 6,750,657 is, however, that they all require a relatively large through-hole and therefore are not suitable for tank installations in which a small through-hole (sometimes as small as having a diameter of 1″-2″ (2.5-5 cm) is used.

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