| 摘要 |
The invention relates to a metal-detection system having transmitting and receiving coils which are arranged relative to one another in such a way that magnetic decoupling prevails, and having an electronic evaluation system. The solution is characterised by a) the measurement of a disturbance in the two-dimensional field using magnetic fields vertically assigned to one another, b) two transmitting coils and one receiver coil and c) phase and amplitude compensation. The metal-detection system according to the invention is distinguished by a thorough digitisation of its subassemblies, which leads to drastic reductions in the problems of drift and guarantees exact reproducibility of the measurement operations. All the trigger pulses and reference signals are obtained from the fundamental frequency (e.g. 10 MHz quartz oscillator) of the transmitter unit. It is thus impossible for the tuning to occur on the basis of temperature variations or aging such as occur with RC-equipped timing elements. The essential novel aspect of the system is represented, however, by the rotating exciting field which eliminates the problems of orientation.
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