Contactless magnetic position sensor of magnetic or electrically conducting objects

摘要

The contactless magnetic position sensor of magnetic or electrically conducting objects according to the present invention consists of at least one excitation coil (10) connected to an alternating signal source (20). A magnetic field sensor (40) having its output connected to the input of an amplifier (60) is located within the excitation coil (10) cavity. The sensor comprises an excitation modulator (21) that is connected to an alternating signal source (20). The amplifier (60) output is connected to the input of a low pass type filter (80), further to the input of a band pass type filter (81), and to the input of a high pass type filter (82). The alternating signal source (20) generates an alternating, preferably rectangular, current and owing to this, an alternating magnetic field is generated near the excitation coil (10). This alternating magnetic field interacts with materials near the excitation coil (10). The magnetic filed sensor (40) can be an anisotropic magnetoresistor AMR or Hall probe. In case of the AMR sensor, the excitation coil (10) driving signal is connected via a decoupling capacitor (30) directly to a flip-flop input of the AMR sensor coil. Thanks to coherent condition of the excitation coil (10) driving and thus also the generated alternating field and modulation of the sensor output through a flip-flop circuit, a controlled rectification of the sensor output signal and proper demodulation of the output signal take place. The sensor output can then be used for sensing a position, detection of approach or discrimination of materials near the coil.