| 摘要 |
PURPOSE:To achieve an expanded metal detectable range and stabilized circuits, by detecting the time at which metal approaches most with an IC oscillation circuit so arranged that the intensity of oscillation varies as the metal approaces and a detection circuit which detects and smooths AC signal outputted from the oscillation circuit. CONSTITUTION:Peak wave detection circuits are added. A peak wave detection circuit 6 which detects peak voltage from the output of a detection circuit 5 is provided and a Schumitt circuit 7 applies hysteresis to a signal outputted from the detection circuit 6. The sensor voltage outputted from the detection circuit 5 decreases as metal approaches and reaches the lowest level when the metal approaches a coil most. As the metal separates away from the coil, the decreased voltage increases to return to the original condition. The time of causing the largest change in the voltage, when the metal approaches most is detected with the peak wave detection circuit 6 and a signal is sent to the Schumitt circuit 7 to indicate the metal passages. Thus, the passage of a metal piece is detected hourly while expanded metal detectable range and stabilized circuits can be promoted. |
