| CPC G01N 22/00 (2013.01) | 8 Claims |

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1. A method for distinguishing between a presence of a foreign body or a gas bubble in a flowable medium in a pipeline or a container, the method comprising:
transmitting microwave signals into the flowable medium;
introducing mechanical vibrations into the flowable medium;
receiving microwave signals that have passed through the flowable medium;
evaluating the received microwave signals and detecting the presence of an object the gas bubble, or the foreign body in the flowable medium via the received microwave signals or a value derived therefrom, wherein the gas bubble present in the flowable medium is set into vibration by the mechanical vibrations, and a modulation of the received microwave signals or of the value derived therefrom is generated by the vibrating gas bubble;
detecting the gas bubble only when mechanical vibrations are introduced and the received microwave signals or the value derived therefrom is/are modulated; and
otherwise, detecting a foreign body.
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