| 摘要 |
1,017,188. Analysing fluids electrically. ESSO RESEARCH & ENGINEERING CO. April 14, 1964 [May 14, 1963], No. 15422/64. Heading G1N. Apparatus for determining the concentration of water vapour in a gas mixture comprises two similar piezo-electric crystals 10,11 (Fig. 3), each coated with a substrate 10a, 11a capable of absorbing the water vapour to change the resonant frequency of the crystal by an amount indicative of the concentration. The crystals are fed periodically with alternate dry gas and test gas mixture, and the difference in resonant frequencies is determined by a mixer 14, to be indicated on a recorder 17. The alternations of dry gas and test gas, produced by a rotating four-way valve 20, eliminate hysteresis effects produced by a direct difference measurement. Different substrates are given for water vapour and for other gases, to be deposited on a magnetostrictive or piezo-electric material. |
