Apparatus and method for contactless measurement of the conductivity of a liquid in a flow channel

The invention relates to an apparatus and a method for contactless measurement of the conductivity of a liquid in a flow channel as well as the use of the apparatus and method. A DOLLAR A device for contact-free (non-electrode) measuring the conductivity of a liquid in a flow channel is known from DE 3718111 C2. There, a current whose intensity is measured by means of a second coil induced across a coil in the liquid. This device is, as regards the manufacture and handling, consuming. DOLLAR A The invention is thus based on the object to provide an apparatus and a method for contactless measurement of the conductivity of a liquid in a flow channel that is easy to handle and is inexpensive as possible. DOLLAR A This object is inventively achieved in that a toroidal coil is closely arranged around the flow channel which is interconnected with a capacitance to form a resonant circuit, and in that the electrical properties of this circuit depending on the desired conductivity are measured.