In order to increase the accuracy of on-line liquid density measurements, a sensor equipped with a tuning fork as the resonant sensitive component is designed in this paper. It is a quasi-digital sensor with simple structure and high precision. The sensor is based on resonance theory and composed of a sensitive unit and a closed-loop control unit, where the sensitive unit consists of the actuator, the resonant tuning fork and the detector and the closed-loop control unit comprises precondition circuit, digital signal processing and control unit, analog-to-digital converter and digital-to-analog converter. An approximate parameters model of the tuning fork is established and the impact of liquid density, position of the tuning fork, temperature and structural parameters on the natural frequency of the tuning fork are also analyzed. On this basis, a tuning fork liquid density measurement sensor is developed. In addition, experimental testing on the sensor has been carried out on standard calibration facilities under constant 20 °C, and the sensor coefficients are calibrated. The experimental results show that the repeatability error is about 0.03% and the accuracy is about 0.4 kg/m3. The results also confirm that the method to increase the accuracy of liquid density measurement is feasible.
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机译：为了提高在线液体密度测量的准确性，本文设计了一种配备音叉作为共振敏感组件的传感器。它是一种结构简单，精度高的准数字传感器。该传感器基于共振理论，由一个敏感单元和一个闭环控制单元组成，其中敏感单元由执行器，谐振音叉和检测器组成，并且该闭环控制单元包括前置电路，数字信号处理和控制单元，模数转换器和数模转换器。建立了音叉的近似参数模型，并分析了液体密度，音叉位置，温度和结构参数对音叉固有频率的影响。在此基础上，开发了音叉液体密度测量传感器。另外，已经在标准的校准设备上在20°C恒定温度下对传感器进行了实验测试，并且对传感器系数进行了校准。实验结果表明，重复精度约为0.03％，精度约为0.4 kg / m 3 。结果也证实了提高液体密度测量精度的方法是可行的。
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