Design And Realization Of SF₆ Sensor Based On The NDIR Technology

SF6 gas has excellent insulation and interrupter performance and is widely applied to electrical systems. However, once electrical equipment suffers SF6 gas leakage, the gas and its decomposition products may not only pollute the environment but also influence safe operation of the electrical equipment and even harm the health of workers. Therefore, the detection of SF6 gas concentration in the electrical system is of vital importance.In order to satisfy the actual need of accurate measurement of SF6 gas concentration in the electrical system,a kind of miniaturized high performance non-dispersive infrared SF6 sensor is designed and realized according to the infrared spectrum absorption theory and with single-beam dual-wavelength differential absorption detection technology in this thesis. In the optical system, the compactness and stability is improved significantly by replacing the traditional mechanical chopper type modulated light source with the new electrically modulated infrared source. A pyroelectric infrared detector integrating high-precision optical filter is employed to realize photovoltaic conversion. This, coupled with dual output of the measurement channel and the reference channel, increases the detection precision and anti-interference ability of the sensor. The gas chamber is produced with the advanced 3D printing technology, which is helpful for realizing miniaturization and high precision of the sensor. In the circuit system, a drive circuit is designed based on the working characteristics of the light source, with which the electrical modulation of the light source is realized and the working stability of the light source is improved. Based on the working features of the detector, a signal conditioning module is designed reasonably, achieving functions like weak output signal amplification,rectification,filtering,etc. of the detector. With single-chip system as the control core, the system realizes signal acquisition, data processing, serial communication, light source modulation, etc.In the experiment,SF6 gas with standard concentration is adopted to calibrate the sensor and the curve of relation between SF6 gas concentration and output voltage is fitted out. The experiment results show that the sensor system we design can accurately detect SF6 gas concentration within 0-2000ppm, and the repeatability,stability and detection error of the system can all meet the expected requirements.This SF6 sensor features miniaturization, long service life, low cost, fast response, etc.and has a wide application prospect in electrical industry, etc.