Department of Automotive Science, Graduate School of Integrated Frontier Science, Kyushu University, Nishiku, Fukuoka 819-0395, Japan.
Department of Advanced Energy Science and Engineering, Kyushu University, Kasuga, Fukuoka 816-8580, Japan.
Rev Sci Instrum. 2023 Mar 1;94(3):035001. doi: 10.1063/5.0113877.
An absolute gas concentration can be measured from the variation in the speed of sound between two gases in principle. Owing to the small difference in the speed of sound between the atmospheric air and oxygen (O) gas, measuring O concentration with high accuracy in the humid atmospheric air using ultrasound needs careful investigation. The authors show successfully a method to measure the absolute concentration of O gas in humid atmospheric air using ultrasound. It was possible to measure O concentration in the atmospheric air with accuracy by compensating for the influence of temperature and humidity by calculation. The O concentration was calculated from the conventional speed of sound equation by utilizing small mass variation for the change in moisture as well as temperature. This method using ultrasound enabled us to measure the O concentration in the atmospheric air as 21.0%, which is in agreement with the standard atmospheric dry air. The measurement error values after the humidity compensation are about 0.4% or less. Furthermore, this method takes only about a few ms for measuring O concentration and, thus, can be used as a high-speed portable O sensor for industrial, environmental, and biomedical instruments.
从理论上讲，可以通过测量两种气体之间声速的变化来测量绝对气体浓度。由于大气空气中的声速与氧气（O）气体的声速差异很小，因此需要仔细研究如何在潮湿的大气空气中使用超声波高精度测量 O 浓度。作者成功展示了一种使用超声波测量潮湿大气空气中 O 气体绝对浓度的方法。通过计算可以补偿温度和湿度的影响，从而可以精确测量大气空气中的 O 浓度。通过利用湿度变化和温度变化的小质量变化，从传统的声速方程计算出 O 浓度。该超声法使我们能够以 21.0%的比例测量大气空气中的 O 浓度，与标准大气干燥空气一致。湿度补偿后的测量误差值约为 0.4%或更小。此外，该方法测量 O 浓度仅需几毫秒，因此可用作工业、环境和生物医学仪器的高速便携式 O 传感器。
