| 摘要 |
The damping of a coil (L1) can be influenced by an object (1) so that the high-frequency voltage at the coil (L1) depends on the distance (a) of the object (1) from the coil (L1). A constant dc current is superimposed on the high-frequency current through the coil, the dc voltage drop at the coil (L1) which corresponds to the dc resistance of the coil (L1), damping the coil (L1), being influenced by the temperature. The high-frequency excitation (5, 6) of the coil (L1) is controlled by the dc voltage drop in order to compensate for the influence of the temperature on the high-frequency voltage so that the high-frequency voltage depends solely on the distance (a). The high-frequency voltage, having a nonlinear correlation to the distance (a), is linearized in a nonlinear member (15) with a semiconductor element with respect to the distance (a). In this connection, the effect of the temperature on the linearization is compensated for by means of a second semiconductor element.
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