Two-channel metal detector, having two sets of perpendicularly oriented sensor antennas, is proposed to expand detectable size,\nranging from mm through cm scale, of metal sensor, while conventional metal sensor is dedicated for detection only in mm or\ncm scale. The characteristics of the two metal detection sensor channels were investigated, respectively, and the interference effect,\nwhile in simultaneous operation, between two sensor channels was discussed. Metal detection channel, having sensitivity in mm\nscale, showed detectable sensitivity to moving ferrous sphere, with diameter down to 0.7 mm, at 50 kHz exciting frequency and\nenhanced sensitivity distribution. And metal detection channel having sensitivity in cm scale showed more uniform sensitivity\ndistribution with the flexibility for future modular construction. The effect of interference, while in simultaneous operation of two\nsensors, resulted in reduced output response, but still within usable detection range. Thus it was feasible to operate two sensors,\nhaving different sensitivity range, simultaneously and to extend detection range frommmto cm scale, within practically acceptable\ninterference.
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