The accuracy and reliability of the metal detectors machine depends on the stability of the electromagnetic transmitter frequency. Generally, the operating frequency from 80 to 800 kHz is used. The lower the working frequency, the better the detection performance of iron; the higher the working frequency, the better the detection performance of high carbon steel. The sensitivity of the detector decreases with the increase of the detection range, and the size of the induced signal depends on the size of the metal particles and the conductivity.
Due to the current pulsation and current filtering, the metal detectors machine has certain restrictions on the transport speed of the detected items. If the conveying speed exceeds a reasonable range, the sensitivity of the detector will decrease.
In order to ensure that the sensitivity does not decrease, the appropriate metal detectors machine must be selected to suit the corresponding detected products. Generally speaking, the detection range should be kept as small as possible. For products with good high-frequency inductance, the detector channel size should match the product size. The adjustment of detection sensitivity should be determined with reference to the center of the detection coil, and the center position has the lowest induction. The detection value of the product will change with the change of production conditions, such as changes in temperature, product size, humidity, etc., which can be adjusted and compensated through the control function
Balls have repetitiveness, the smallest surface area, and the most difficult to detect for metal detectors machines. Therefore, the ball can be used as a reference sample for detection sensitivity. For non-spherical metals, the detection sensitivity largely depends on the location of the metal. Different locations have different cross-sectional areas, and the detection effect is also different. For example, when passing longitudinally, iron is more sensitive; while high-carbon steel and non-iron are less sensitive. When passing horizontally, iron is less sensitive, while high-carbon steel and non-iron are more sensitive.
In the food industry, systems usually use higher operating frequencies. For food such as cheese, due to its inherent high-frequency induction performance, it will increase the response of high-frequency signals proportionally. Moist fat or salt substances, such as bread, cheese, sausage, etc., have the same conductivity as metals. In this case, in order to prevent the system from giving false signals, the compensation signal must be adjusted to reduce the sensitivity of the induction.