MAKING A METAL DETECTOR

"ALL ARTICLES IN THIS SECTION ARE FOR INFORMATIONAL PURPOSES ONLY AND THEY ARE WRITTEN IN A WAY THE READERS CAN UNDERSTAND THE BEST. "

Developments in the electronics technology allows people to engage in various electronics experiments for hobby purposes. This allows people to build door bells, automatic night lights, simple alarm systems, water heaters, regulators, or simple robots, making use of a few easy to use circuits. In addition, amateurs in the field claim in such posts that detectors can be produced just like fixing an electronic device such as a radio or a television. One should note the following point first: Such information provided would not suffice to build a detector. They do not dwell upon the expertise and R&D requirements, as well as the substantial investments required for building detectors, as they tend to ignore numerous details in the production stage. You can use the information available on the Internet to build a very crude system that would make a sound or light a led when a metal is brought close. These do not look so complicated for people with sufficient electronics skills. However, they would not serve any purpose other than a feeling of satisfaction received from achieving a purpose. Expecting more would be a mistake.

Detectors produced on mass production lines at production plants, on the other hand, are of a completely different breed. Firms set a purpose for the detector in the design stage. A team of software engineers prepare the software and calculate the algorithms required to achieve that purpose. Both safety and sturdiness is taken into account when determining the equipment required. Consistent and stable operation of the device, minimum susceptibility in the face of hot and cold temperatures, adaptability to different soil (surface) compositions, and ensuring the safety of the user are a direct function of the focus on such details. Each part, from the battery to the processor, would be tested hundreds of times over different surfaces, at different temperature levels. The information revised on the basis of test results would be updated frequently, and the design would be finalized to ensure most optimal and stable product.

The products sold today by well-known brands is the product of at least 10 engineers' years of efforts in software, hardware and testing. While detectors produced in simple workshops do not try to achieve sensitivity or any balance, a detector produced in mass production plants will be subject to strict procedures where a deviation in the range of millimeters may lead to a complete replacement of the whole project.

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The ability of a professional metal detector to operate on various terrain, to discriminate metals, and depth capability should be taken into account. These are what the specialists producing these devices focus most on. Some of the equipments and methods used in detector design and production are dedicated to this business, since small details in detector production may lead to substantial difference in the results achieved.

As the operating frequencies used in VLF band (3-50 KHz) devices of both mechanical and electronic designs do not require a substantial basis in radio frequencies, therefore, a sensitivity level of milliseconds would be just fine to perceive the impact a medium sized metal would create. Hobby circuits would be capable of providing such sensitivity levels. However, spotting the same soil, and discriminating it among other metals, would require a sensitivity level to account for nanoseconds in latency and calculations. For instance; A 15KHz VLF induction equilibrium system takes into account a 0.1 degree phase margin without losing any depth soil. This corresponds to a range of 18.52 nanoseconds in the total phase scale. In addition, given that at least 16 bits sampling is required for digital analysis of the phase margin in question, at a 3V reference measurement, a voltage difference of approximately 46 microvolts arise. Even though 16 bits is not a very large number for A/D transformer, obtaining the necessary sampling rate required to operate "analog" and "mixed signal" elements to work at this signal level, at an acceptable noise rate, requires substantial focus on design.

In addition to an accurate digitization of the signals, mathematical analyses and syntheses to interpret them requires non-linear differential analyses, which is a tad beyond what analytical mathematics of classical engineering offers, and should be done in real-time. It is relatively easy to get basic functionality through a simple circuit, not only for VLF, but also for pulse injection. Yet, measurement and analysis of time constants of the reaction voltage from the eddy current, to allow determination of depth and metal type with adequate performance, requires a significant focus on engineering calculations. The professional sensitivity levels of modern devices requires R&D and an unabated will for design.

Even though a detector you can produce in a workshop by applying your basic electronics expertise may offer some basic detection function, the practical use of such devices would be very limited. If you seek to build a device you can use in the field, the process would be comparable to trying to make a washing machine, television, or computer at home. Considering the device would be used outdoors, that it would get some shaking at your hands, and that it has to protect fine tuning to a level of millimeters, building a detector may, after all, be more difficult than the abovementioned devices.

Therefore, it should be safe to assume that a detector built by amateurs in make-shift workshops and using uncertified materials, would not have any commercial value, and these devices should be avoided.



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