Proximity switch - working principle

The inductive sensor consists of three parts: oscillator, switching circuit and amplification output circuit. The oscillator generates an alternating magnetic field. When a metal target approaches this magnetic field and reaches the sensing distance, eddy currents are generated in the metal target, causing the oscillation to attenuate and even stop. The changes in the oscillator's oscillation and oscillation are processed by the post-stage amplifier circuit and converted into switching signals, which trigger the drive control device to achieve non-contact detection purposes.

2. Working principle of capacitive proximity switch

The sensing surface of the capacitive proximity switch consists of two It is composed of coaxial metal electrodes, much like "open" capacitor electrodes. The two electrodes form a capacitor and are connected in series in the RC oscillation circuit.

When the power is turned on, the RC oscillator does not oscillate. When a target approaches the capacitor's electricity, the capacitor The capacity increases and the oscillator starts to oscillate. Through the processing of the downstream circuit, the vibration and oscillation signals are converted into switching signals, thereby achieving the purpose of detecting the presence of objects. The sensor can detect both metal objects and non-metal objects. The maximum action distance can be obtained for metal objects. The action distance for non-metal objects depends on the dielectric constant of the material. The greater the dielectric constant of the material, the greater the action that can be obtained. The greater the distance.

3. Working principle of Hall switch

Magnetic switch is a proximity switch, which (even through non-ferrous metals) respond to a permanent magnetic field. The operating distance is larger than that of the inductive proximity switch. The response curve is related to the direction of the permanent magnetic field.

When a target (permanent magnet or external magnetic field) approaches, the magnetic permeability of the coil core (the inductance of the coil The quantity L is determined by it) becomes smaller, the inductance of the coil also decreases, and the Q value increases. The oscillator is excited to oscillate and the oscillation current is increased. When a magnetic target approaches, the current consumption of magnetic sensors [1] increases.