| 摘要 |
<p>PURPOSE:To enable a metal detector to detect the passing of very small metallic impurities while noise signals are generated and the polarity of the signals is not inverted by constituting the detector in such a way that the detector is provided with a detecting means and differentiating means and outputs a metal detecting signal when the detector detects the minimum and maximum values of signals generated by the fluctuation of an induced voltage. CONSTITUTION:A metal detector is constituted in such a way that differentiating means 9 and 10 are provided after unbalanced signal detecting means 7 and 8 and the detector outputs 20 a metal detecting signal only when the minimum value of signals is detected when a prescribed period of time has elapsed after detecting the maximum value of the signals caused by the fluctuation of the induced voltage first detected by the means 9 and 10, Since the maximum and minimum sections of the signals are detected 7 and 8 and metal detecting signals are outputted 20 when the maximum and minimum sections exist even when the polarity of the signals is not inverted (from the maximum value to the minimum value), the passing of small metallic impurities can be detected 16, 19, and 20 even when the impurities pass while noise signals are generated. Therefore, not only the influence of noise can be, removed, but also metallic impurities can be surely detected. When a saturated state detecting means 21 is provided, in addition, even the passing. of large-sized metallic impurities can be surely detected.</p> |
