Single-Sensor Metal Double-Sheet Detector Principle

1. Principle for single-sensor detection of magnetic materials (iron and other ferromagnetic materials):

The overall schematic is shown below; the judgment is made using the principle of electromagnetic induction.

When there is no material under the probe, the controller generates a high-voltage square wave. The square wave passing through the coil and core inside the probe produces a mostly open magnetic field; at this time the native current feedback in the driver chip has little phase deviation from the square wave.

When a ferromagnetic material is placed tightly under the probe, the probe's coil, core and the surrounding magnetic material form a mostly closed magnetic circuit. According to Lenz's law and Faraday's electromagnetic induction law, this closure increases the magnetic flux through the coil, causing the induced current to increase; the driver chip's feedback native current then shows a larger phase deviation from the square wave and the native current magnitude decreases.

In practice, the controller records the native current values for no-load and for a single sheet of material; during measurement it compares the measured value with the recorded native currents to determine single-sheet versus double-sheet conditions.

2. Principle for single-sensor detection of non-magnetic materials (aluminum, copper and other non-ferromagnetic materials):

The overall schematic is shown below; this uses the eddy current principle.

When there is no material under the probe, the controller excites the driver chip with a high-frequency sine wave; the alternating current through the probe coil generates an alternating magnetic field, and the driver chip feeds back the original voltage amplitude.

When a non-ferromagnetic material is placed tightly under the probe, the high-frequency alternating magnetic field induces eddy currents on the material's surface due to the skin effect. These eddy currents generate an alternating magnetic field that interacts with the coil, causing changes in coil inductance L or impedance ZL, which in turn reduce the driver chip's feedback voltage amplitude.

In practice, the controller records the original voltage amplitudes for no-load and for a single sheet of material; during measurement it compares the measured value with the recorded voltages to determine single-sheet versus double-sheet conditions.

Atonm (Guangzhou) Intelligent Technology Co., Ltd. focuses on the research and development of Metal Double-Sheet Detectors and is committed to providing high-precision overlap-detection solutions across multiple industries. Our single-sensor series of Metal Double-Sheet Detectors are widely used in automotive, automotive parts, metal sheet processing, home appliances, batteries and metal packaging industries for contact double-sheet detection.

To meet customer needs in various application scenarios, Atonm has refined its contact-type single-sensor Metal Double-Sheet Detector series into multiple professional models, including:

1. Full-metal single-sensor Metal Double-Sheet Detector (integrated ferromagnetic and non-ferromagnetic design): model MDSC-9000S

2. Ferromagnetic-version single-sensor Metal Double-Sheet Detector: models MDSC-8000S, MDSC-8200S

3. Non-ferromagnetic-version single-sensor Metal Double-Sheet Detector: models MDSC-8100S, MDSC-8300S

We are committed to improving detection accuracy and efficiency through technological innovation to help customers achieve higher production standards and quality control. If you have overlap-feeding issues, please contact Atonm for a customized solution and support.