The working principle and structure of the metal detector

In 1960, the world's metal detector was born. The original metal detector was mainly used in industry and mining. Its function was to check the purity of minerals and improve efficiency. After decades of development, metal detectors have undergone several generations of changes in detection technology. From the earliest signal simulation technology to the digital pulse technology used today, metal detectors have undergone tremendous technological changes. The resolution, sensitivity, detection accuracy, and performance have all undergone a qualitative leap, and the scope of application has become more and more extensive. Now metal detectors are widely used in food. Next, let's take a look at the working principle and structure of the metal detector. Here are some answers.

Here is the content list:

• How the metal detector works.

• The structure of the metal detector.

How the metal detector works.

The metal detector uses the principle of electromagnetic induction to generate a rapidly changing magnetic field using a coil with alternating current passing through it. This flux will induce eddy currents within metal objects. The eddy current generates a flux, that successively affects the first flux, inflicting the detector to beep. The current flowing through the transmitting coil generates an electromagnetic field, just as a motor also generates an electromagnetic field. The polarity of the magnetic field is perpendicular to the plane of the coil. Whenever the current changes direction, the polarity of the magnetic field will change accordingly. This means that if the coil is parallel to the ground, the direction of the magnetic field will alternate continuously, perpendicular to the ground down for a while, and perpendicular to the ground up again for a while. Because the direction of the flux changes repeatedly within the ground, it'll act with any semiconducting target it encounters, inflicting the target itself to get a weak flux. The polarity of the flux of the target is precisely the other of the polarity of the flux of the transmission coil. If the direction of the flux generated by the transmission coil is perpendicular to the bottom downward, the target flux is perpendicular to the bottom upward.

The structure of the metal detector.

A typical metal detection system consists of four main components, namely the detection head, control panel, transmission system, and automatic rejection system. The metal detector coil, or called the detection head, has a built-in "balanced coil". Three coils are wound on a non-metal frame or forming device. The coils are completely parallel to each other. The coil (transmitting coil) in the middle generates a magnetic field through a high-frequency current. The two coils located on both sides of the middle coil are receiving coils. Since these two coils are the same and keep the same distance from the transmitter, their induced electromotive force is the same. Once these coils square measure connected in reverse, the voltage cancels one another out, so forming a "zero output", that is, reaching a state of equilibrium. Then it's poured with cement to make sure that once no product passes through, the flux is in a very dynamic equilibrium state, and isn't laid low with external environments like temperature changes, vibration, and magnetic attraction interference. During the detection, the product passes through three coils one after another. If it contains metal foreign objects, the balance of the magnetic field will be broken, and induced current will be generated to detect various metal foreign objects.

The user interface or control panel of the metal detector, commonly including touch screen type and button type, is generally installed directly on the detection head. However, if the detection head is too small, or is installed in an inconvenient or inaccessible place, it can be installed remotely using a connecting cable. The transmission system of the metal detector is used to pass the product through the opening. The most commonly used transmission device is the horizontal conveyor belt. At the same time, for different product applications, you can choose the gravity drop type (powder or particles transported in the pipeline), the horizontal pipeline type (liquid and fluid), and plastic guide grooves commonly used in the pharmaceutical industry. The automatic rejection system of the metal detector is used to reject any infected products out of the production line. It is usually installed on the transmission system. There are many different types, including blowing type, push rod type, flap type, etc. The type of rejection system will depend on the product to be tested.

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