Metal detector circuit diagram,The metal detector is a relatively simple device, an electronic circuit that provides good sensitivity and stability. A distinctive feature of this device is the low operating frequency. Metal detector coil operates at a frequency of 3 kHz. It provides, on the one hand, and poor response to unwanted signals (such as signals that occur in the presence of wet sand, and small pieces of metal, etc.), on the other hand, good sensitivity when looking for water pipes hidden and manages central heating, coins and other metal objects.
The birth of metal detector coil is fluctuations in transport at a frequency of about 3 kHz, making the magnetic field rotates. Receiver coil is perpendicular to the coil refers to going through the magnetic field lines create a EMF. Received signal output coil either absent or very small. Metallic object entering the coil field, change the value of the inductor and output an electrical signal, which is then amplified, rectified and filtered. Thus, the output signal of a system is an ongoing effort which a little when approaching a coil of metal body increases the value. This signal is fed into one entry from the comparison, and are compared with the reference voltage that is applied to the input of the second. Voltage signal level adjusted so that even a slight increase in the reference voltage to change the State of the output of the comparator. This in turn lead to electronic switches, which led to the amplifier output stage has a warning to inform the operator of a metal object.
The second integration makes the “saw” signal is coming very close to sinusoidal in shape and consists of a parabolic half wave. This stable signal going to the power amplifier, a conversion of the current effort, “and loaded on the sensor coil. Sensor voltage is not stable capacitance and signal reflected from metal objects. The absolute value of this instability is very small. To increase it, which distinguishes a useful signal, the compensation service and integration II output voltage of the voltage across the sensor coil.