Conductance Measurement of Water Vapor by the Time-Ratio Method

There are currently few methods available to measure the conductance of water vapor through an orifice. The feasibility of the pressure rising method to measure the conductance of water vapor is analyzed by combining theory with experiment，indicating that the measurement error of this method increases with the decrease of intake volume，which is due to the strong adsorption characteristic of water vapor. To accurately obtain the relationship between the conductance of water vapor and the inlet pressure，a new method called the time-ratio method is proposed. This method calculates conductance by measuring the time of pressure change，reducing the effect of water vapor adsorption on the measurement effectively. Based on this method，a device is developed to provide a flow rate in the range of 3. 7×10-9~1. 5×10-5 Pa·m·3 s-1. The measurement and theoretical values of conductance have good consistency，and the relative standard uncertainty of this time‑ratio method is 3. 3%. © 2024 Northeast University. All rights reserved.