Abstract
Two-channel metal detector, having two sets of perpendicularly oriented sensor antennas, is proposed to expand detectable size, ranging from mm through cm scale, of metal sensor, while conventional metal sensor is dedicated for detection only in mm or cm scale. The characteristics of the two metal detection sensor channels were investigated, respectively, and the interference effect, while in simultaneous operation, between two sensor channels was discussed. Metal detection channel, having sensitivity in mm scale, showed detectable sensitivity to moving ferrous sphere, with diameter down to 0.7 mm, at 50 kHz exciting frequency and enhanced sensitivity distribution. And metal detection channel having sensitivity in cm scale showed more uniform sensitivity distribution with the flexibility for future modular construction. The effect of interference, while in simultaneous operation of two sensors, resulted in reduced output response, but still within usable detection range. Thus it was feasible to operate two sensors, having different sensitivity range, simultaneously and to extend detection range from mm to cm scale, within practically acceptable interference.
Highlights
The metal detection sensor is widely used in food processing industry and defense industry [1, 2] to detect metal pieces in surrounding object, and considerable efforts have been devoted to enhance sensitivity and selectivity
Metal detection sensor, using electromagnetic wave, usually is strongly influenced by nearby electromagnetic wave which is within several times of sensor width; it is not feasible to place a second sensor in the vicinity of the first sensor
Two-perpendicular-antennas model is introduced to Journal of Sensors minimize physical interference, and the optimal signal detection method is investigated to reject the interference between metal sensors having different sensitivity resolution
Summary
The metal detection sensor is widely used in food processing industry and defense industry [1, 2] to detect metal pieces in surrounding object, and considerable efforts have been devoted to enhance sensitivity and selectivity. Other methods are envisaged to detect these materials which are not detectable by using metal sensor Among these foreign materials, the detection for metal pieces is important [5] in food industry, and various researches are concentrating on this. This paper is concerned with the experimental development of two channel metal sensors by cascading two metal sensors having different sensitivity resolution with minimum interference with each other. Two-perpendicular-antennas model is introduced to Journal of Sensors minimize physical interference, and the optimal signal detection method is investigated to reject the interference between metal sensors having different sensitivity resolution
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