Metal ( Metal )- The device with which you can find metal objects in a neutral or weakly conducting medium. The metal detector can detect metal in water, soil , in wood, in the walls, under your clothes , in food. etc. According to the principle of
metal detectors such as " send-receive ».The principle of their action is based on two inductors - reception and transmission . The coils are arranged so that the output signal from the transmitter coil , from detecting the host . If the device appears near a metal object , the signal transmitting coil re-emit in all directions. After the dispersion of the signal detected by the receiving coil. The receiving coil amplifies the received signal and sends to the display unit .
Advantages: relatively simple circuitry, a large range to adjust for different media types and search for metal.
Disadvantages: the complexity of manufacturing the sensor , a significant sensitivity to the mineralization of the soil.
Induction metal detectors .is a variety of devices such as " send-receive ", but unlike them contain only one coil . It also serves as a transmitter and receiver. The main problem in creating such metaloiskateley is the difficulty of separation of the reflected signal is relatively small compared with the powerful radiated . Advantages: simple design of the sensor.
metal detectors - frequency meters .It is based on LC- oscillator frequency . When approaching the metal object to the circuit , its frequency changes . This change is recorded by various methods.
Pros : Simple sensor design , relatively simple circuitry .
Disadvantages: Worst recognition capabilities found objects rather low sensitivity .
Pulse metal detectors- work on the classical principle of pulse induction. The transmitter generates a transmitter coil current pulse . The transmitter coil creates a swirling around a magnetic field. This field induces a current in the metal object ( object detection ) . After switching off the current in the transmitter coil , an induced current in the metal objects does not disappear immediately, but decays over time . That is, the object is created around the secondary vortex magnetic field . This field induces a voltage pulse in the receiving coil detector.
Advantages: deadbands to mineralized ground , the simple design of the sensor .
Disadvantages: some effect on the device to electromagnetic pulses.