一种(10^(-5)-10^(-16))Pa·m^(3)/s标准气体流量计的设计

Anovel Design of Standard Gas Flowmeter with Therange of (10^-(5)-10^(-16)) Pa·m^(3)/s

本文设计出下限为5×10^(-16)Pa·m^(3)/s的标准气体流量计,解决了超灵敏度检漏仪的量值溯源难题。采用基于固定流导法基本原理的标准气体流量计,通过激光打孔和镀膜制备的分子流导元件,成功获得下限为10^(-10)m^(3)/s的分子流导;采用电容薄膜真空计作为参考标准测量压力,将直接供气、膨胀衰减压力及标准混合气体三种方法集成在一起,为流导元件入口获得(10^(3)-10^(-6)) Pa的示漏He气分压力;采用10^(-8)m^(3)/s和10^(-10)m^(3)/s量级的两套分子流导元件,结合流导元件入口压力获得了(10^(-5)-10^(-16)) Pa·m^(3)/s的标准气体流量,设计的标准气体流量计估计合成标准不确定度为1.2%-2.8%。

The standard gas flowmeter with the lower limit of 5 × 10^(-16)Pa · m^(3)/s is designed to solve the traceability of measurement value for ultra-sensitive leak detector. The flowmeter is designed based on the constant conductance method,and the range of it is decided by the conductance of the molecular flow element and the inlet pressure of the element. The molecular flow element with the conductance of 10^(-10) m^(3)/s can be achieved by laser drilling on a platinum sheet and vacuum coating process,and the inlet partial pressure range of helium from 10^(3) to 10^(-6) Pa can be reached by combining three methods,which are the direct gas supply method,the expansion method,and the mixed gas preparation method. The standard gas flowmeter can provide gas flow with the range of( 10^(-5)-10^(-16)) Pa·m^(3)/s only using the capacitance diaphragm gauge as reference pressure standard and two molecular flow elements with the conductance of 10^(-8) m^(3)/s and 10^(-10) m^(3)/s. And the combined standard uncertainty of the flowmeter is estimated to be 1. 2% to 2. 8%.