The accuracy and reliability of the metal detector depend on the stability of the electromagnetic transmitter frequency, which generally uses the working frequency from 80 to 800 kHz. 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 induction signal depends on the size of the metal particles and the conductivity.
Due to the current pulsation and current filtering, the metal detection machine has a certain limit on the speed of detection. If the conveying speed exceeds the reasonable range, the sensitivity of the detector will decrease.
In order to ensure that the sensitivity does not decline, it is necessary to select the appropriate metal detector to adapt to the corresponding products to be tested. Generally speaking, the detection range should be controlled to the minimum value as far as possible. For the products with good high frequency induction, the channel size of the detector should match the product size. The adjustment of detection sensitivity should refer 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 temperature, product size, humidity, etc., which can be adjusted and compensated through the control function
Globules have repeatability, minimum surface area, and are the most difficult to detect for metal detection machines. Therefore, the sphere can be used as a reference sample for detection sensitivity. For non spherical metals, the detection sensitivity depends largely on the position of the metal. Different positions have different cross-sectional areas, so the detection effect is different. For example, when passing longitudinally, iron is more sensitive; high carbon steel and non-ferrous are less sensitive. Iron is not very sensitive to transverse passage, while high carbon steel and non-ferrous are more sensitive.
In the food industry, the system usually uses a higher operating frequency. For example, cheese food, due to its inherent high-frequency induction performance, will proportionally increase the response of high-frequency signal. Wet fat or salt substances, such as bread, cheese, sausage, etc., have the same electrical conductivity as metals. In this case, in order to prevent the system from giving wrong signals, the compensation signal must be adjusted to reduce the induction sensitivity.
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