Design And Analysis Of Pulse Underground Metal Detector Circuit

- Oct 11, 2019-

In order to study the effect of VFTO on electrical insulating materials, a fast pulse metal detector for simulating VFTO is designed. The output waveform of the detector requires that the rise time is 50ns and the peak voltage is 1000 kV. The generator consists of Marx generator, load test chamber and intermediate connection section. Marx uses positive and negative charging circuits, including 10 0.015 uF/100kV plastic shell capacitors and 6 spark gap discharge switches. A 500_high resistance is connected in parallel at the load end to accelerate the oscillation attenuation speed of output high voltage pulse and reduce the insulation requirement of equipment, thus compacting Marx structure and reducing the inductance of discharge circuit. At the same time, capacitors and spark switches in Marx generator adopt special reentry wiring to further reduce the inductance of discharge circuit. The design scheme of the fast pulse generator is also given. The Pspice simulation results show that when the output voltage is 1000 kV, the rise time varies from 23 to 28 ns in the actual range of load variation, which meets the requirements.

20130911171959_34830

There are many circuits, such as pulse-induced metal detectors, which appear on the Internet. Although they process signals in different ways and generate magnetic field pulses, these electronic devices are basically the same. Its main part is the coil that generates the magnetic pulse.


The size of the coil mainly depends on the required detection depth and the minimum size of the detected object. Generally speaking, it can be said that the coil diameter of the theoretical maximum detection depth is five times that of the minimum size of the object detected by the coil. This is the most valuable and heavily dependent situation. It's obvious that you can't detect objects 5 centimeters deep with a one-meter coil. But what kind of coil do you need? That's a specific question. Many people use metal detectors to search for coins and jewelry. In these cases, a 25cm or 40cm coil is enough. In my case, I need to locate a 20 cm iron lid at a depth of two meters or a metal-filled china. That's why I want to make a 1 meter coil. Although the physical size and shape of coils may vary (square or elliptical coils are used to work the same but preferably circular under certain circumstances), there are only slightly different physical designs between inductance coils. The optimum inductance range of the search coil for the commonly used pulse induction metal detector is 300 to 500 uH. In this design, I will assume that the coil used is 400 mH. For smaller coils, it means more loops need to be wound.

1-160111105931a6

Based on the analysis of various narrow pulse generation methods, a new type of ns-level high voltage narrow pulse metal detector is developed by using the oscillating circuit principle. It can output an adjustable ns-level pulse voltage with a pulse width of 20-100 ns and an amplitude of 500-1 000 V. The parameters of each device in the theoretical and simulation analysis circuit show that the obtained ns-level high voltage pulse waveform is smooth and symmetrical. Ultra-wideband UWB is a kind of ultra-narrow pulse utilizing nanosecond level. The technology of transmitting information is discussed. A UWB extremely narrow pulse generator with cascaded avalanche transistor structure is discussed. The circuit and the working principle of the avalanche transistor are analyzed in detail. The output pulse width of the UWB is about 1.22ns and the rise time is about 863ps.


Pulse Gold Detector coil design; there are many circuits, which appear on the Internet pulse induction metal detectors; coil size mainly depends on the depth of detection required and the detected object; coil is powered by commonly used batteries; when voltage passes through a high-speed bipolar transistor or MOSFET, the electricity; total resistance in MOSFET to negative power supply is determined; now, I. They have defined the inductance and resistance of the coil, but the coil is in; coil size; size; 120 mm; 150 mm; 175 mm; 200 mm.