| 摘要 |
PURPOSE:To detect the ground surface magnetic field buried in the peripheral noise with a high precision, by using a feference signal, which is outputted from a reference signal oscillator, to perform the synchronous detection. CONSTITUTION:A signal output terminal 3 is connected to the conductor of a communication cable to be detected, and the output signal of an oscillator 1 for transmission where the current is made constant by a constant current equipment 2 is flowed to the conductor to generate a magnetic field, and a magnetic field sensor 4 consisting of a search coil or the like is used to detect the magnetic field. The magnetic field sensor 4 coverts the detected magnetic field to an AC signal, and this signal is amplified by a selective amplifier 5 and is applied to a synchronous detector 8 through a signal input terminal 9. In the synchronous detector 8, a reference signal which is applied from a reference signal oscillator 6 through a phase shifter 7 and has a certain phase relation to the output signal of the oscillator 1 for transmission is used to detect synchronously the output signal of the selective amplifier 5, and the output is displayed on an output display 11. |
