Technology On Detecting And Processing Of Photoelectric Signal Of Dual-channel Fiber Optic Air Pressure Sensor

Sensing technology is one of the high-techs that are compelling and develop rapidly. And fiber-optic sensing technology is applied in more and more areas due to its outstanding advantages. Air pressure sensors are widely used in areas like weather reporting, automobile manufacturing, chemical industry, spaceflight, food producing, electronic encapsulation and scientific research. So, on the basis of knowing the dynamic of fiber-optic sensors in and abroad, especially the status quo and development of reflected intensity modulation(RIM) fiber optic detecting, the detecting and processing technology of photoelectric signal based on the dual-channel fiber optic sensor used in air pressure measuring is dissertated in this paper. The circuit system as well as its realization is introduced.The signal processing circuit of this system mainly consists of a photoelectric detecting circuit, a band pass filter (BPF), a TRMS converting circuit, an amplifier at the last level and the MCU application system. The BPF is the key part that eliminates the noise of the system. The transmission function and the amplitude-frequency characteristic of the filter is deeply analyzed. This filter guarantees the system precision as the components of the BPF were picked with choice. An AD736 chipset is used in the TRMS circuit. This chipset is very suitable for this sensing system because it is of high precision, good sensitivity and high speed. Been processed by the above steps, the two signals of the two channels are then sent to the A/D unit which consists of a 12-bit TLC2543 A/D converter to have them converted into digital. The digital results are subsequently sent to the MCU to have further processing steps with software. The quotient of the two signals is acquired in the MCU. After the non-linear rectification, the measuring result is finally displayed on the LCD. The software flow chart as well as some key subprogram is given in this paper.The calibration experiment of the system was done. Some commonly used non-linear rectifying methods are presented. The experimental data are processed with MATLAB7.0 and the fitting curve of experimental data is given. As the experiment indicates, the measuring scale of this sensor introduced in this paper is 900～1100hPa.