| 摘要 |
<p>SAMPLING METAL DETECTOR A sampling type of metal detector is described in which an oscillator transmits an oscillator signal current through the transmit coil of the detector to produce an electromagnetic field in the region of a search head. A received signal is induced in the receive coil of the detector when a metal object is present within that portion of the electromagnetic field which is external to the search head. A sampling pulse generator produces sampling pulses, at a time related to the output signal of the oscillator, which are transmitted to a sampling circuit for sampling the received signal. In the preferred embodiment, the received signal is sampled at a time controlled by a phase shift adjustment means to produce an output sample voltage such that any indication due to mineral soils or other background conditions is excluded from the sample.</p> |
