Research on Tuning Fork Dimension Optimization and Density Calculation Model Based on Viscosity Compensation for Tuning Fork Density Sensor

Abstract

At present, real-time online measurement of fluid density is of great significance to improve the automation level of petrochemical and food industries. The tuning fork density sensor is widely used because of its characteristics of real-time online measurement, high measurement accuracy, simple structure, and convenient use. The traditional tuning fork density sensor in the market has the disadvantage of low resolution and being susceptible to liquid viscosity, which makes the sensor’s measurement accuracy low and not suitable for the measurement of high-viscosity liquid density. The measurement resolution and antiviscosity interference capability of the tuning fork density sensor are two major indexes to measure the measurement performance of the sensor, among the antiviscosity interference capability refers to the degree to which the measurement results of the sensor are affected by viscosity properties. However, the structural design of the tuning fork density sensor results in the conflict between the measurement resolution and the antiviscosity interference capability of the sensor, and the improvement of one performance is bound to affect the performance of the other. Aiming at the problem of how to balance the measuring performance of the tuning fork sensor, a density calculation model based on viscosity compensation is proposed in this paper. By studying the working principle and structure design of the tuning fork, the vibration characteristics of tuning fork in liquid with different viscosities and densities are modelled and simulated. From the results of simulation analysis, the better set of dimensions with balanced measuring performance is selected. Not only does the structure of the tuning fork have the characteristics of high resonance frequency, but also the measured results are less affected by the viscosity of the liquid. To solve the problem that density measurement is still affected by high-viscosity liquid after tuning fork dimension optimization, in this paper, the partial least square model is used to fit the experimental data of the frequency-density characteristics; then, the density calculation model based on the viscosity compensation is obtained by combining the frequency-viscosity characteristic experiment. Finally, through the performance test experiment comparing with the traditional tuning fork density sensor, the measurement resolution of the improved tuning fork density sensor is as high as 0.0001 g/cm3; within the viscosity range of 180 MPa·s, the accuracy reached ±0.001 g/cm3, and within 480 MPa·s, the measurement accuracy reached ±0.002 g/cm3. When the liquid viscosity reaches more than 10 MPa·s, the improved tuning fork density sensor has better overall measurement performance than the traditional tuning fork density sensor, and both of its measurement resolution and antiviscosity interference capability have been greatly improved.

Design of a Transformer Oil Viscosity, Density, and Dielectric Constant Simultaneous Measurement System Based on a Quartz Tuning Fork

“…Traditional methods of measuring transformer oil viscosity and density include fluidbased calculations, ultrasound, and Raman spectroscopy, but these methods have some limitations, such as requiring the use of expensive and bulky equipment, only being able to monitor one or two parameters at the same time, and not being able to fulfill the need for real-time monitoring [10]. In recent years, resonant sensors have been introduced for the measurement of fluid density and viscosity.…”

A non-reference detection method of the external ultrasonic liquid level switch using the PZT

“…There are many LLS technologies including: floating ball LLS [5], cable float LLS [6], capacitive LLS [7], tuning fork LLS [8], ultrasonic LLS [9], external ultrasonic LLS [10], etc. Among them, the external ultrasonic LLS is a new type of level measurement alarm device, which is installed outside the tank, no need to open holes in the tank, and non-contact measure.…”

New Measurement Method of Viscosity, Density, and Dielectric Constant of Transformer Oil Based on Quartz Tuning Fork

“…There are many traditional methods for detecting insulating oil, such as classical fluid calculation, ultrasonic method, and Raman spectroscopy. However, under normal circumstances, these measurement methods are expensive and bulky, and can only measure one or two parameters at a time, which cannot well meet the real-time requirements [19]. In contrast, the method of using a quartz tuning fork for measurement has low cost and small volume, and can measure three parameters simultaneously online, which is suitable for parameter detection of transformer oil.…”