| 摘要 |
PURPOSE:To make circuit constitution simple and equilibrium adjustment setting easy, by testing the existence of mixed metals by detecting magnetic flux detection difference signals from a center-earthed secondary coil with a detector controlled by the 0 deg. and 90 deg. phases of an oscillator. CONSTITUTION:A detector head 10 consists of the oscillator coil L1 of a transmitter 11 and center-earthed secondary coils L2 and L3 of a receiver 12, and when a metal mixed tested object passes between the transmitter 11 and the receiver 12, magnetic flux detection difference signals are generated in the coils L1 and L2. These difference signals, via a phase transfer circuit 50, are detected by detectors 31 and 32 which open when the phase of an osicllator 13 is 0 deg. or 90 deg., and if a detector output ratio given by a divider 70 passes a prescribed value, a metal mixture detection signal is outputted by a window comparator 71. Therefore, the configuration is simplified, and at the same time, the accurate phase setting of the coils L2 and L3 become unnecessary. In addition, if the detector output is subtraction, multiplication and root mean square processed, the same result can be obtained, and if the magnetic flux of the coil L1 is inclined and judgement setting values are selected, the effect of minute magnetic flux changes generated by other substances than metals can be prevented. |
