Metal Detectors  Manufacturers, Traders, Suppliers

Metal detectors are indispensable in the military, to find hidden mines and ammunition, but they are also used in other areas of industry. Other hidden metal parts, pipes and electrical conductors can be found. Metal detectors are search instruments for metallic materials. They locate non-visible metal, for example pipes, electrical conductors and other metal parts. This type of detector is usually battery-powered and equipped with electronic circuits. Furthermore, they have a search coil whose magnetic field should reach as far as possible. The coil itself has a flat or stretched shape. One speaks here also with a plate or ring form without core. A flat form is therefore used, for example, to search people or floor areas. In addition, you can follow the course of lines and cables in the ground and in walls. The search system is based on various measurement methods. Firstly, the pulse measurement. They were used to periodically transmit individual current pulses. These impulses in turn generate eddy currents in metallic materials in the environment. These are picked up by the coil. These currents cause a change in the signal in the receiving coil. This can be measured when the pulse is switched off. Depending on the length and strength of the pulse sequences, the size and type of metallic objects can be deduced. These signals are usually evaluated in the time domain. The principle of alternating current measurement is also applied. In most cases, a low-frequency signal of the alternating current in the frequency range of a few 10 kHz is emitted continuously. This allows analysis according to amplitude and phase position in the spectral range. A magnetically coupled system is used for transmission. Metallic objects, but also electrically conductive liquids, cause a change in the amplitude and phase position received in relation to the transmitted signal. These two independent parameters make it possible to distinguish between different materials and metallic objects. Further substances can also be classified by using different transmission frequencies which are emitted simultaneously. Devices that work according to this principle usually use the so-called resonance method. The different resonances of the different metals and substances are related to the density of the substances. Primary influencing factors for differentiation are magnetic permeability and electrical conductivity. Non-metals differ considerably from metals in these material consonants. The mobility of the load carriers is also important. The signal change is electronically evaluated in all measuring procedures and made visible on an optical scale or audible by an acoustic signal transmitter above a certain threshold value. In industrially used metal detectors, for example in the food industry for quality assurance and to avoid metal splinters in food, the signal evaluation is used for automatic control of the production position.