Kazys R, Rekuviene R, Sliteris R, Mazeika L, Zukauskas E
Ultrasound Research Institute, Kaunas University of Technology, Barsausko st. 59, Kaunas LT-51368, Lithuania.
Rev Sci Instrum. 2015 Jan;86(1):015003. doi: 10.1063/1.4905570.
A novel ultrasonic measurement technique for density measurements of different liquids in extreme conditions has been developed. The proposed density measurement method is based on transformation of the acoustic impedance of the measured liquid. The higher accuracy of measurements is achieved by means of the λ/4 acoustic matching layer between the load and the ultrasonic waveguide transducer. Introduction of the matching layer enhances sensitivity of the measurement system. Sometimes, the density measurements must be performed in very complex conditions: high temperature (up to 200 °C), pressure (up to 10 MPa), and high chemical activity of the medium under measurement. In this case, the special geometry metal waveguides are proposed to use in order to protect the piezoelectric transducer surface from influence of a high temperature. The experimental set-up of technique was calibrated using the reference liquids with different densities: ethyl ether, ethyl alcohol, distilled water, and different concentration (20%, 40%, and 60%) sugar-water solutions. The uncertainty of measurements is less than 1%. The proposed measurement method was verified in real conditions by monitoring the density of a melted polypropylene during manufacturing process.
一种用于在极端条件下测量不同液体密度的新型超声测量技术已被开发出来。所提出的密度测量方法基于被测液体声阻抗的变换。通过负载与超声换能器波导之间的λ/4声匹配层实现了更高的测量精度。匹配层的引入提高了测量系统的灵敏度。有时，密度测量必须在非常复杂的条件下进行：高温（高达200°C）、高压（高达10MPa）以及被测介质的高化学活性。在这种情况下，为了保护压电换能器表面免受高温影响，建议使用特殊几何形状的金属波导。该技术的实验装置使用具有不同密度的参考液体进行了校准：乙醚、乙醇、蒸馏水以及不同浓度（20%、40%和60%）的糖水。测量不确定度小于1%。通过监测制造过程中熔融聚丙烯的密度，在实际条件下验证了所提出的测量方法。
