Method And Standard Equipment Development Of Small Gas Flow Rate Measurement

With the wide applications of the standard gas in the fields of environmental monitoring, chemical industry, electronics industry, and aeronautics and astronautics, etc, reliable calibration and traceability of the gas measurement attract more attentions. However, current small gas flow traceable standard equipments are lack and expensive. Therefore, it is of great significance to investigate the methods and to develop the standard equipment for small gas flow rate measurement.An economic measurement method of gas flow is proposed based on the Bernoulli equation for compressible fluids, which accords to the investigation on some results and the comprehensive performance of a variety of cases of small gas flow rate standard measurement equipment with the characteristics of automatic and high-precision, the analysis and comparison of the structure and principle of the classic equipment, considering various problems existed in the measurement process. The measurement principles of critical flow venture nozzle flow are described, and a regulator method used to realize the high-precision measurement for small gas flow rate on the basis of mainly research on measurement method of key parameters, a fuzzy-PID frequency voltage control system to ensure the stability of the pressure is designed. Then, a PLC-based gas flow standard equipment with the positive pressure method is developed based on sonic nozzle method and PVTt law, the range of detection is from6×10-3Nm3/h to6Nm3/h. Finally, the uncertainty of this standard equipment is analyzed.Method and standard equipment development for small gas flow rate measurement will lay a solid foundation for higher precision measurement by using small gas flow rate.