Research on the low-frequency weak signal detection method based on MFB topology filters

Raw signals in nature often appear in a very weak way, the general means of detection is through special sensors or electrodes directly or indirectly in contact with the signal medium to be tested, the converted electrical signals are amplified and filtered for processing and then accessed to the terminal for the analysis and storage of data [1]. Due to the complexity of the environment, testing different variables requires the use of different test devices. Based on the above considerations, this paper independently designed a low-frequency weak electrical signal detection device based on MFB topology filtering and instrumentation amplification. In the device sensor input using PJ-392 interface, the interface supports 3. 5mm audio coaxial cable, with good low noise transmission characteristics and versatility. The pre-stage uses a high-quality instrumentation amplifier INA118, which significantly improves the common mode rejection ratio and amplifies the differential mode signal; the intermediate stage adopts a high-order MFB topology filter, which can effectively filter out the environmental high-frequency noise; the post-stage adopts an industrial frequency trap, which eliminates the industrial frequency noise brought by the utility cable; in terms of the power supply, the use of a dual-charged pump to provide a negative power supply, which reduces the complexity of the power supply system; through the optimization of the hardware, the The use of small package devices improves the integration of the instrument. In this paper, the processor is used for the corresponding acquisition, processing and output display of the converted signal. The validation shows that the device has a good ability to capture low-frequency weak signals and strong noise suppression performance, which effectively realizes the bioelectricity detection, tiny fixed frequency vibration detection, infrasound detection and other functions. It can be widely used in industry, precision detection and other fields.