#metal detector frame
Metal detectors are used for various purposes, depending on their type.
Detectors are widely used in security systems — to detect weapons and explosives.
Characteristics of metal detectors
The metal detector device is designed to determine and classify the metal present.
Let's consider the characteristics of metal detectors of various types, among which are:
— simple, ground metal detectors;
— semi-professional;
— professional ground;
— metal detectors for searching for gold nuggets;
— underwater;
— deep;
— arch (or frame) and hand-held inspection metal detectors.
We will consider the latter separately a little later.
Semi-professional metal detectors operate on the principle of using multi-frequency radiation.
They can operate not only with sound, but also with visual information. On the display, you can see the detected object with a distinction between non-ferrous and ferrous metals. Professional ground metal detectors are used for experienced searches.
The characteristic of a professional type metal detector is that it has multi-voice discrimination, a multi-frequency search range, and many manual and automatic settings.
The device is able to distinguish a colored object from a black one with an accuracy of up to 80%.
This allows for a more accurate search in places where there is a lot of household iron waste.
Professional metal detectors use visual, digital and sound signaling when detecting a signal.
Such metal detectors operate on the principle of digital signal processing by a microprocessor.
Deep metal detectors are a solid search technique capable of detecting an object at a depth of up to 2.5 meters.
Objects such as pipelines, large-volume metal structures, such a metal detector detects up to 6 meters. However, such a detector is not capable of detecting an object located at a shallow depth.
This type of metal detector does not have a discrimination function, which makes it necessary to dig up the object.
The most complex technical characteristics of a metal detectoris inherent in the pinpointer, since this device is aimed at the most accurate search for an object.
The accuracy of determining the location of an object varies from 1 mm.
Pinpointers are not equipped with discrimination and are designed to detect inside wall wiring.
Metal detector frame
What is the mechanism of operation of the metal detector frame?
Here we will have to remember something from the school physics course.
Inside the external search coil of the metal detector — the transmitting frame — there is a wire through which an electric current moves, creating an electromagnetic field.
The direction of movement of the magnetic field changes with the change in the direction of movement of the current.
Any metal object located nearby, from the influence of a changing magnetic field, will begin to produce electric currents.
The induced current, in turn, will create its own magnetic field, with a direction opposite to the magnetic field of the transmitter, which is how it will “reveal” itself.
Inside the outer frame of the metal detector there is another coil, located in such a way as to maximally neutralize the influence of the transmitting coil.
This is called a receiver. But the field from a nearby metal object will induce a current in the receiving coil, which can be amplified and processed electronically, having first been separated from the more powerful signal of the transmitter.
The received signal is usually captured with some delay compared to the transmission of the emitted signal.
This is due to the fact that conductive materials have the ability to resist both the flow of electric current itself and changes in the magnitude of the current already flowing in them. This delay is also called a «phase shift».
Maximum phase shift will be produced by objects that are mostly inductive — these are large, thick objects made of excellent conductors.
An important criterion for the characteristics of a detector is the quality of discrimination — recognition and classification of detected objects.
In the metal detectors, installed at facilities to ensure transsecurity, this criterion plays an important role.
Since passers-by and passengers can carry quite «harmless» metal objects, it is impossible to allow unnecessary waste of time on searching a person.
Inspection metal detectors
Equipment for detecting metal objects during personal inspection of a person — inspection metal detector is familiar to anyone who has ever been to a nightclub.
Such detectors are used by law enforcement officers, customs officers, the military, and security and safety services.
The inspection procedure itself is part of the security guard's job responsibilities.
Some inspection metal detectors can be configured to detect objects of various sizes, even very small ones. The fact of detection of metal objects in the metal detector's control zone is carried out by a sound, light or vibration signal.