As consumers pay more attention to the food safety, there are more and more complaints related to the presence of foreign matter in food. According to statistics, about 50% of food quality complaints are foreign matter complaints.

In order to detect foreign matter in food, large food companies are basically equipped with metal detectors or X-ray machines. The X-ray foreign matter detector for food is to generate X-rays through the equipment and apply the penetrating ability of X-rays to detect metal foreign matter and non-metal foreign matter with high density mixed in the product. In addition, food X-ray machines can also carry out the product missing detection, damaged packaging detection, and weight detection, but the cheapest ones are all over $20,000. For small and medium-sized food companies, especially small food companies, it is difficult to afford. While the price of metal detectors in China is around $2,500 to $5,000, which is relatively affordable for small and medium-sized food companies.

The food metal detector is used to detect metal foreign matter mixed in the production process of food, medicine, cosmetics, and textiles. Currently, 95% metal detectors of the market are balanced coil metal detectors, the principle is a central transmitting coil and two equivalent receiving coils, these three coils are installed in a detection head, and the oscillator emits a high-frequency magnetic field through the transmitting coil in the middle, which is connected to the two receiving coils, however, the polarities are opposite. When the magnetic field is not disturbed by the outside world, the voltage output signals they generate cancel each other out. Besides, once metal impurities enter the magnetic field, this balance will be disrupted, and the metal detector can detect the presence of metal.

The lower the operating frequency of the metal detector (25kHz--800KHz), the lower the sensitivity of the device, and the higher the frequency, the higher the sensitivity of the device, this phenomenon is very obvious to non-ferrous metal. The low frequency is used for wet products and metal film packaging products, and high frequency is used for dry products. When a single-frequency operated metal detector is used for both dry and wet products, the sensitivity will be reduced.