振动管式液体密度检测方法的探讨

STUDY ON MEASURING METHOD OF LIQUID DENSITYBY A VIBRATING TUBE SENSOR

介绍了振动管式液体密度计的工作原理，以及自行研制的悬臂梁式Ｕ型石英玻璃管式液体密度计的结构，采用集中参数法对其振动方程进行了推导，设计了信号采集与处理系统，并对整个测量系统进行了试验分析。结果表明，所设计的振动管式液体密度计工作稳定、测量精度高。通过误差分析发现，温度是造成测量误差的主要原因。

The measuring technology of liquid density is mainly used in the management of vehicle petroleum and the analyses of wine, oil, drink and water in food engineering. The traditional methods of density measurement, such as the static weighting method, the density bottle method and the floating instrument method, are complicated and difficult for spot analysis. So, an investigation in a small vibrating tube densimeter for on line use was conducted. At first, the principle of the meter was analyzed based on its elastic mechanics and the nonlinear relationship between the oscillating frequency and the liquid density was inferred by means of the lumped parameter method. Besides, the authors also designed a circuit used for gathering the signals, amplifications, filtering waves and for changing phases, calculations and display. A U type quartz glass vibrating tube liquid densimeter was studied and manufactured and the experiments on the densimeter were carried out. The results show that the meter has a high accuracy and the temperature is the main cause for measuring error that is compensated by a compensatory parameter. Finally, some methods were recommended for on line measurement. The conclusions are: (1) the vibrating tube should be tightly connected to the base; (2) the size of the vibrating tube should be equalized and the material used for the tube should have a good elastic characteristic; (3) a great attention should be paid on the influence of temperature.