Electromagnetic Compatibility Requirements and Test Methods for AC Stabilized Power Supply
Usually the metal detector is composed of two parts, namely the metal detector and the automatic rejecting device, among which the detector is the core part. There are three sets of coils distributed inside the detector, that is, the central transmitting coil and two equivalent receiving coils. The oscillator connected to the middle transmitting coil generates a high-frequency variable magnetic field. In the idle state, the induced voltage of the receiving coils on both sides Before the magnetic field is disturbed, they cancel each other out and reach a balanced state. Once metal impurities enter the magnetic field area and the magnetic field is disturbed, this balance will be broken, and the induced voltages of the two receiving coils cannot be offset, and the induced voltages that have not been offset will be amplified and processed by the control system, and an alarm signal will be generated (metal impurities detected ). The system can use the alarm signal to drive the automatic rejecting device, etc., so as to exclude metal impurities from the production line.
According to the transportation mode of the detected items, metal detectors are usually divided into: channel type, drop type and pipeline type.
Channel Metal Detector
At present, the most common metal detection equipment on the market is channel-type metal detector. The channel of the detector is square, and it is generally equipped with a conveyor belt mechanism, with an automatic rejecting device, or provides an alarm signal. When the items on the conveyor belt pass the detector, once there is metal, it will be automatically rejected or stop conveying. It is mainly aimed at the online inspection of finished and semi-finished products, and provides the final inspection before shipment.
For example: bagged materials, boxed products, etc.
Falling body metal detector
Falling body metal detectors generally have automatic rejection devices, so it is customary to call them falling body metal detectors, or metal detectors.
Metal detectors must not contain metal in the packaging of the product, but considering the high requirements for sealing and light protection, it must be packaged with a metal composite film. The metal composite film itself is metal, so if a channel-type metal detector is used, the detection sensitivity will have a large deviation, or even cannot be detected. For the above reasons, testing before packaging is an option. The falling body metal detector was developed for the above situation and is mainly used for the detection of tablets, capsules, granular (plastic particles, etc.), and powdery items. When these items fall through the falling body metal detector, once metal impurities are detected, the system immediately starts the separation mechanism to eliminate suspicious items. It has the characteristics of simple installation, high sensitivity, convenient maintenance, high efficiency, stability and reliability.
Pipeline Metal Detector
Ordinary metal detectors cannot completely monitor the entire production process of fluid products, such as sausage meat sauce, chewing gum, oral liquid, etc., and remove metal impurities online in real time to ensure that the products are transported to the next process. Under normal circumstances, these products are packaged in metal, and they generally cannot be detected by metal detectors after they become finished products. In addition, liquid or viscous items are detected before canning or packaging, which can effectively improve the detection accuracy.
Whether it is the food, pharmaceutical and rubber industries, or the textile, paper, mining and recycling industries, we can supply a metal detector or separator to meet their requirements. In addition to the above-mentioned three main forms of channel type, drop type and pipeline type, there are also pipeline type and flat plate type suitable for air-driven vacuum transportation.
Tablet:
It is usually used to detect products with relatively thin thickness but relatively large width and length, such as woven fabrics and extruded sheets. Its primary purpose is to protect downstream equipment, such as cutting tools, calendering systems, etc.; at the same time, to improve product quality.
Metal detectors and separators are generally independent of installation orientation and can be installed horizontally, vertically and obliquely, almost anywhere in the production process.
