Research On The Standard Device Of Small Gas Flow Based On Laminar Flowmeter

Gas micro flow measurement technology is widely used in semiconductor processing,automotive electronics,medical and other industries.However,the calibration/calibration techniques of related flowmeters are still relatively lacking.Research on standard devices based on laminar flow meters,the main work and results are as follows:(1)Research on the new gas laminar flow sensing technology.Aiming at the nonlinear problem of capillary flow inlet section and inlet and outlet local resistance of traditional laminar flow method,a differential and pressure differential laminar flow sensing method is proposed.The principle analysis of differential and pressure differential laminar flow sensing technology is carried out.The pressure loss of each part of the sensing unit pipeline in these two laminar flow sensing technologies is analyzed.The pressure loss curve is drawn and proved.The flow and pressure loss of the two new laminar flow sensing elements are better in line with the linear relationship,that is,Hagen-poiseuille law designed and processed differential and pressure differential laminar flow sensing units to perform flow-The experimental results of differential pressure test are in good agreement with the theory.(2)Design and development of gas small flow standard device based on pressure difference method laminar flow sensing unit.The overall scheme and test pipeline design of the gas small flow standard device based on the pressure difference method laminar flow sensing unit was carried out.The standard device flow range(0.08-30)m3/h.The integrated modular pressure differential gas laminar flow sensing element was designed and processed,and the differential pressure transmitter,PLC controller,frequency converter and fan were selected.The measurement and control system design and development and PC software development were completed,and the overall system assembly and debugging was completed.(3)Testing and calibration of the developed gas flow standard device.The laminar flow measurement unit in the developed flow device was calibrated using a sonic nozzle flow standard device and a gas bell flow standard device.The flow range of the sonic nozzle and the bell flow standard device calibration experiment was 0.08-5 m~3/h and 0.5-30m~3/h,respectively.the two sub-passages have overlapping areas for convenient use.After calibration,the developed gas small flow standard device meets the design flow and uncertainty requirements.