A metal detector is a tool designed to detect metal objects. A metal detector can detect metals by the physical principle of electromagnetic induction and the formation of eddy currents.
History of the Metal Detector
Alexander Graham Bell made in 1881 a simple metal detector. This was used to find a bullet in the body of the murdered president James Garfield. A portable metal detector was only developed much later. In 1931 the German-American engineer Gerhard Fischer was granted a patent on a portable detector. He initially designed the portable detector to look for metal ores. It soon became clear that the metal detector was also very useful for the defense. In the Second World War, the portable metal detectors were widely used for mine detection.
Quality of metal detectors
Metal detectors are available in many different types and sizes nowadays. The diversity is enormous and ranges from amateur detectors to highly professional detectors. The quality of it is determined on the basis of a number of points. An important aspect is its character distinctiveness. This is also called a discrimination function. For example, a simple detector will be difficult to distinguish iron from other (nobler) metals. The professional ones have an extensive discrimination function and can also offer a good distinction when two different metals are next to each other. Another important aspect for a metal detector is the depth range.
This is also very different per metal detector. Usually, large-sized metal objects are found at a maximum of 30 cm. Larger objects can be found at a depth of 1 meter by a good detector. User-friendly metal detecting devices have a clear display on them, the user of the metal detector can read a lot of information. For example, different types of metal can be displayed in a code and an indication of the probable depth of an object can also be displayed. These are all aspects that promote the ease of use of the metal detector.
The weight and ergonomic shape of a metal detector are also important. You can also look at the volume and the frequency. Relatively new is the possibility to search completely underwater with it. Usually, the display is hardly resistant to water. The Garrett At Pro and the Minelab Excalibur can be used underwater. Despite that, there are differences between the Minelab Excalibur and the Garrett At Pro. Especially the Minelab Excalibur is a detector that is widely used by divers. These detectors are used, among other things, for metal detection in shipwrecks or when wading through water.
Each metal detector has specific characteristics and that ensures that someone does or does not choose a certain detector brand or detector type. Some of them are used on the beach with good soil balance in connection with mineralization. For arable land, there are also such devices with a good discriminatory function. For militaria seekers, the detection of iron is more important than for searchers looking for coins. Due to these different wishes and requirements, various types of detectors have been developed over the years.
Different types of metal detectors
There are metal detectors, as you have read above, in different shapes and sizes. Mostly, people talk about portable metal detecting devices when talking about metal detection. However, there are many more different types of detectors. For example, there are metal detection gates at, for example, airports and buildings that have to be monitored for special reasons.
Visitors to these metal detection gates must pass through a gate or under an arch. In the arch or gate, there are various electronic systems like iPod, keychains, knifes that ensure that metals are detected through the clothing of the visitors. Personnel can get information (by visual means) or on screens (visual) about the amount of metal that the visitor has with him or with her.
If there are doubts about the detected metal, there is usually a smaller metal detector that can be used by a security officer to determine the exact location of the metal.
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