Patent ID: 6100820
Filing Date: 2000-08-08
Classification: G01V

Abstract:
A vehicle detector comprising:a sensor comprises an inductive loop, having a first terminal and a second terminal,an oscillator circuit which excites said inductive loop,a sampling circuit which determines an operational status of said inductive loop, andan evaluator that is connected to the sampling circuit for purposes of deriving a detector signal that corresponds to the instantaneous status of the inductive loop,wherein said oscillator circuit comprises:a fixed-frequency generator, which has a first terminal and a second terminal, wherein said generator first terminal is connected to said inductive loop first terminal and sends a transmit signal to excite said inductive loop, anda phase/amplitude controller, which is arranged between said fixed-frequency generator and said inductive loop second terminal, wherein said inductive loop second terminal has a summation point for purposes of supplying a compensation signal, whereina bridge circuit is formed by said inductive loop, said fixed-frequency generator and said phase/amplitude controller, which is balanced at zero voltage at said summation point in a resting state of said inductive loop, and that said sampling circuit, which is connected to said summation point, is implemented as a voltmeter.