Doubt relating the phenomena

Asked by Akash Choudhary | 19th Feb, 2012, 10:30: PM

Expert Answer:

Metal detectors use one of three technologies:

  • Very low frequency (VLF)
  • Pulse induction (PI)
  • Beat-frequency oscillation (BFO)

sampling circuit in the metal detector is set to monitor the length of the reflected pulse. By comparing it to the expected length, the circuit can determine if another magnetic field has caused the reflected pulse to take longer to decay. If the decay of the reflected pulse takes more than a few microseconds longer than normal, there is probably a metal object interfering with it.

The sampling circuit sends the tiny, weak signals that it monitors to a device call an integrator. The integrator reads the signals from the sampling circuit, amplifying and converting them to direct current (DC). The direct current's voltage is connected to an audio circuit, where it is changed into a tone that the metal detector uses to indicate that a target object has been found.

Answered by  | 20th Feb, 2012, 01:12: PM

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