The principle of the drug metal detector is a central transmitter coil and two equivalent receiver coils. The three coils are housed in a probe. The oscillator emits a high-frequency magnetic field through the transmitting coil in the middle and is connected to the two receiving coils. However, the polarity is reversed. In the case that the magnetic field is free from external interference, the voltage output signals generated by them cancel each other out. Once metallic impurities enter the magnetic field region, the balance will be destroyed, the induced voltages of the two receiving coils cannot be canceled out, and the unsuppressed induced voltage is amplified by the control system. The metal detector can detect the presence of metal and generate Alarm signal (metal impurities detected). The system can use this alarm signal to drive automatic reject devices and the like to remove metal impurities from the production line.
The accuracy and reliability of metal detectors for medicines depends on the stability of the frequency of the electromagnetic transmitters. Generally, operating frequencies from 80 to 800 kHz are used. The lower the operating frequency, the better the iron detection performance; the higher the operating frequency, the better the detection performance of high carbon steel. The sensitivity of the detector decreases as the detection range increases, and the size of the sensing signal depends on the size of the metal particles and the conductivity.
Pharmaceutical metal detector structure composition
A typical metal detection system consists of the following four main components:
1, the detection head
The detector coil, or detector head, has a built-in "balanced coil." The three coils are wound around a non-metallic frame or former. The coils are completely parallel and the middle coil (transmission coil) passes through a high-frequency current to generate a magnetic field. Two coils located on both sides of the middle coil are receiving coils. Since these two coils are identical and maintain the same distance from the transmitter, their induced electromotive force is exactly the same. When these coils are connected in the opposite direction, the electromotive forces cancel each other, thereby forming a "zero output", ie, reaching an equilibrium state. Then, it is poured with cement to ensure that the magnetic field is in a state of dynamic equilibrium when no product passes through, and is not affected by external environments such as temperature changes, vibration, and electromagnetic interference. The product passes through the three coils in succession. If a metal foreign object is contained, the balance of the magnetic field will be broken and an induced current will be generated to detect various metallic foreign materials.
2, the control panel
The user interface/control panel, commonly known as touch screen and push-button, is usually mounted directly on the test head. However, if the detection head is too small, or if it is installed in a location where traffic is inconvenient or inaccessible, it can be remotely installed using a connection cable.
3, transmission system
The transmission system is used to pass the product through the opening. The most common transmission device is the horizontal conveyor type. At the same time, for different product applications, the gravity drop type (powder or particles in the pipeline) and the horizontal type (liquid and fluid) can be selected. As well as the plastic channel commonly used in the pharmaceutical industry.
4, automatic rejection system
Automatic rejection system for removing any infected product from the production line and is usually installed on the transmission system. There are many different types, including blow type, push rod type, flap type, etc. The type of reject system will depend on the product that needs to be tested.