Who doesn’t dream of stumbling upon something really unusual? After all, our world is full of exciting secrets just waiting to be uncovered. Many simply aren’t prepared to rely on chance, and opt for state-of-the-art metal detectors for a journey of discovery instead. The use of metal detectors is becoming increasingly popular and is the perfect, exciting hobby for the whole family – children, like adults, can become enthusiastic explorers with a metal detector. You can find interesting information about metal detectors here.
What is a metal detector?
As the name suggests, metal detectors help with the location of metallic objects. People who use them to search for objects are known as ‘metal detectorists’. The principle behind metal detectors is easy to explain: An electromagnetic field is generated in a search coil, which the operator moves over the ground while searching. When the field hits an object, it changes. This is detected by the electronic component in the metal detector and the find is indicated by a signal tone or optical signal.
In addition to private use, metal detectors are also used in many other fields, including:
People screening We’re all familiar with the security checks at airports – no one is allowed to board a plane without first being screened by a metal detector.
Testing of food, medicines, etc. Even the best machine will exhibit signs of wear over time. Metal detectors are important tools in ensuring that metal chips do not find their way into products during manufacturing.
Archaeology During excavations, metal detectors can help with the exploration and recording of archaeological sites.
Trade You can never quite tell where pipes and wires are located in the walls of your home. Metal detectors can be used to help locate them and to prevent unwanted damage.
Explosive ordnance disposal Metal detectors can help to locate and professionally remove land mines, unexploded bombs, ammunition, etc.
Structure and function types of the metal detector
Metal detectors always comprise an electronic circuit and a search coil, through which low-frequency alternating current flows. The components are connected to one another by a cable and mounted to a shaft that should, ideally, be length-adjustable. The aim is always to generate a magnetic field that can reach as far as possible. This is achieved with different shapes of search coil – flat coils in ring, plate or double-D shape are mostly used for people screening and ground searches. By contrast, elongated versions are suitable for cavities such as shafts or rock fissures.
In terms of their function, metal detectors are divided into two principal measuring methods:
1. Pulse measurement With this method, pulses of a magnetic field are emitted at specific time intervals. If metallic objects are located in the vicinity, eddy currents are generated within them. Once it has emitted the magnetic pulse, the metal detector switches to receive mode. The eddy currents then cause a change in the signal that can be directly measured as a voltage. In order to determine the size of the object and the metal type of the object, the time progression as well as the duration of the eddy current responses to pulse sequences and pulses of different lengths are evaluated. 2. Alternating current excitation This method uses an uninterrupted alternating current in the coil. Here, two different methods are distinguished:
a. The first is the attenuation analysis, where a low-frequency signal of approx. 10 kHz is emitted. The received signals are constantly analysed to determine their amplitude and phase position. Changes to these two values when compared to the transmitted signal offer an indication of the material and size of the metallic object. b. The second is the BFO technique, where two oscillators constantly emit electrical signals at two different frequencies. The superimposition of the two frequencies creates an acoustic signal that changes in pitch as soon as a metallic object is located nearby.
Analogue or digital – which metal detector is the right one to use?
Metal detectors are available as both analogue and digital devices. As with so many other decisions, what you choose will depend on your specific needs. Here is a brief look at the benefits and drawbacks of the two types:
More accurate measurements
Information about metal type only possible via acoustic signal
Variety of setting options for differentiating between different materials
Number of setting options limited
More weight due to more complex measurement technology
More lightweight design
Higher power consumption
More energy efficient
More complex in operation
Easier to operate
To summarise, an analogue metal detector is perfectly suited as an entry-level device. They're also great for introducing children to the fascinating hobby, as they are both lightweight and easy to use. By contrast, professional metal detectorists often prefer to use digital metal detectors, as they offer more measurement options and more accurate values.
Finding the right metal detector – tips for searching
Has the thirst for adventure got the better of you and you’re looking to buy your first metal detector? The following are some important criteria to keep in mind:
Weight One aspect that must not be underestimated when choosing a suitable metal detector is its weight. After all, once the passion is there, you’ll no doubt want to spend as much time as possible enjoying your new hobby. Every gramme of weight saved will relieve the arm that holds the metal detector.
Ease of use As with any new hobby, you’ll want to score interesting results as quickly as you possibly can. So a metal detector that’s easy to operate is a must. Analogue metal detectors, or digital metal detectors with a higher degree of automation, can bring plenty of enjoyment.
Search depth (also depth performance, search performance or locating depth) Many interesting objects have been lying in the ground for a long time and are accordingly not directly below the surface. The maximum search depth of a metal detector indicates how deep the metallic objects may lie in the ground so that the metal detector can still locate them. At this point, 25 cm for coin-sized objects and 80 cm for larger objects are considered average values. Practical: Some metal detectors can also indicate how deep the located item actually lies in the ground.
Adjustable sensitivity It’s useful to be able to adjust the sensitivity of your metal detector, particularly in difficult soil conditions, such as heavily mineralised soils. That way, you can prevent faulty signals.
Pinpoint mode Some metal detectors offer a pinpoint function, so that you can easily identify the precise location of an object. After all, if a metallic object has been in the ground for a long time, it will start to look like the ground around it, and actually locating it can be challenging.
Wearing comfort Moving a metal detector back and forth over the ground over a long period of time can become exhausting, and it’s important to consider comfort when deciding what to buy. Some metal detectors have padded handles, for example, and ergonomically shaped shafts that can be adjusted to your body size.
Headphone jack If your hunt is in an area with a high level of background noise, it can be worth using headphones. That way, it will be easier to identify changes in the acoustic signals, plus, it’s more considerate to the people around you.
Search coil size The size of the magnetic field also depends on the size of the search coil. A metal detector with a larger coil diameter will allow you to search a much wider area.
Discrimination This function can be used to filter waste and other unwanted objects out of your search. The discrimination function allows you to choose which metals to ignore.
Waterproof coil Anyone considering searching near water should consider opting for a metal detector that can tolerate moisture.
The law – what are you actually allowed to do with a metal detector?
Searching for gold, silver, copper, etc. with a metal detector is a fun and fascinating hobby. Nevertheless, it’s essential that you familiarise yourself with the current legal situation of the area you want to search.
In Germany, the rules differ from state to state, although all states (with the exception of Schleswig-Holstein) allow the use of metal detectors. Anyone searching for non-soil and non-cultural monuments does not generally need to be in possession of a permit. Otherwise, you must apply for an excavation permit from the respective authority responsible for monuments. If you are searching on private property, you must seek the owner’s permission in advance. In Germany the following generally applies: You must report all historical and archaeological finds.
Marked and unmarked archaeological monuments
Cemeteries and graves (also former burial grounds and mounds)
Forests and unmanaged meadows
Historical sites (battlefields, camps)
Provided that you comply with the rules, you should be able to enjoy many hours of fun-filled exploring. We wish you lots of fun and exciting finds!