A
Anonymous
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The larger transmit coil is a very useful feature for it substantially eliminates dynamic range problems. In addition, it increases the depth capability of the detector. A normal coil produces an inverse cubic law with respect to the transmitting signal, which on re-transmission by the metallic object also follows an inverse cubic law. This means that the object also follows an inverse cubic law. This means that the signal sampled by the receiving coil has decreased by an exponential factor of six. In the case of a very large coil, the field is substantially uniform in depth thereby the received signal by the coil has only decreased by an exponential factor of three. This effectively doubles the depth for detectioon of metallic particles as compared with a normal size coil.