恒压式气体微流量计的测控系统研制

Development of Measurement and Control System of Constant Pressure Gas Micro-flowmeter

恒压式气体微流量计的测控系统是在工控机控制下 ,采用电容薄膜规、光电编码器、铂电阻温度计等高精度传感器测量出变容室内气体的压力、体积变化率、温度等参量 ;采用两种恒压控制模式 ,在流量测量的动态过程中将变容室内气体的压力波动控制在± 0 0 1%之内 ;工作软件具有虚拟仪器界面 ,操作方便 ,实现了对流量计的计算机自动化控制和管理。恒压式气体微流量计能够提供 (3 96× 10 -4～ 3 6 4× 10 -8)Pa·m3 /s范围内的气体微流量。在 10 -8Pa·m3 /s范围内的相对合成标准不确定度为 1% ,在 (1× 10 -7～ 1× 10 -4)Pa·m3 /s范围内的相对合成标准不确定度为 0 7%。

In measurement and control system of constant pressure gas micro-flowmeter, the pressure, volume change rate and temperature of gas in variable chamber are measured by capacitance diaphragm gauges, photoelectric coder and platinum resistance thermometer. The fluctuation of pressure in variable chamber is controlled within ±0 01% by a computer with two methods of constant pressure control when gas flow is measured. The software possesses virtual instrument interface and easy operation, which realizes automatic control and management. Measurement range of constant pressure gas micro-flowmeter is from 3 96×10 -4 Pa·m 3/s to 3 64×10 -8 Pa·m 3/s. The related combined standard uncertainty in the range of 1×10 -7 Pa·m 3/s to 1×10 -4 Pa·m 3/s is 0.7%, The related combined standard uncertainty in the range of 10 -8 Pa·m 3/s is 1%.