CN102507369B - A resonant tuning fork liquid density sensor with electromagnetic excitation and detection - Google Patents

Abstract

An electromagnetic excitation detection-based resonant tuning fork liquid density sensor comprises a tuning fork, a fixed support body, a protection tube, two magnetic cylinders, two coils, two fixing members, and a temperature sensor. The protection tube is welded on the fixed support body. The magnetic cylinders and the coils are mounted on the fixed support body via the fixing members, for cooperative use, to constitute an exciter and a detector respectively. The exciter transfers the generated alternating force to the tuning fork via the fixed support body, so that the tuning fork generates simple harmonic vibration according to the natural frequency of the tuning fork, and the vibration signal is acquired by the detector to realize detection of the tuning fork vibration frequency. The vibration frequency of the tuning fork and liquid density are in monotonic function relationship, thus real-time online measurement of the liquid density can be realized. The temperature sensor is attached to the fixed support body to real-time detect the temperature of the measured liquid, so as to compensate change in the modulus of elasticity of the tuning fork. The sensor of the invention can realize high-precision online measurement of various liquid densities at different temperatures.

Description

A resonant tuning fork liquid density sensor with electromagnetic excitation and detection

technical field

The invention relates to a resonant tuning fork liquid density sensor for electromagnetic excitation detection, which is a high-precision resonant quasi-digital sensor, belongs to the field of testing and measuring instruments, and is used for high-precision online measurement of liquid density. The resonant element is a tuning fork.

Background technique

Density is an important physical property of liquids. Measuring liquid density is one of the important means to achieve product quality control in many industries such as medicine, food, petrochemical and so on. Therefore, the measurement of liquid density is of great significance to enterprises. Traditional liquid density measurement methods, such as balance weighing method, density bottle method, float meter method, etc. These methods are mainly manual operation and manual reading. Therefore, it can only be used in discontinuous measurement occasions, and cannot convert physical quantities into electrical signals to realize intuitive digital display and online measurement of the production process, so it cannot realize the automation of production process control.

Since the measurement of liquid density is easily affected by temperature, pressure and liquid viscosity, when measuring liquid density, it is also necessary to accurately measure its temperature, pressure and viscosity. The resonant liquid density measurement sensor is not only simple in structure, small in size, light in weight, and less in wear, but also high in reliability, high in measurement accuracy, high in efficiency, and fast in response. At present, many foreign researchers are studying the use of resonance principle to measure liquid density, such as the 7835 and 7828 density measurement sensors of the British Solartron Electronics Co., Ltd., the 625 type of the American Barton Company, and Japan, Switzerland, Germany, Austria and other countries. Resonant liquid density sensor. However, there are only a very small number of resonant density sensor products in my country, and the methods used mainly include vibrating string method, vibrating tube method, vibrating membrane method and vibrating cylinder method. Among them, the vibrating string method has a complex structure, is easily affected by the mechanical vibration of the environment and liquid flow, and has low precision; the vibrating tube method is more commonly used, but its flow rate is small, the mode shape is asymmetrical, and the vibration frequency is not stable enough; the vibrating membrane method The work is not easy to be stable and the reliability is poor; the vibrating cylinder method has high requirements on the manufacturing process, the uneven wall thickness of the vibrating cylinder can easily make the mode shape asymmetrical, the vibration frequency is unstable, and the viscosity of the liquid will affect the frequency of the vibrating cylinder.

Contents of the invention

The technology of the present invention solves the problem: Overcoming the deficiencies of the prior art, a resonant tuning fork liquid with high measurement accuracy, good stability, high reliability, simple structure, small volume and low power consumption is proposed. density sensor.

Technical solution of the present invention: a resonant tuning fork liquid density sensor for electromagnetic excitation detection includes: tuning fork body, solid support body, protection tube, first magnetic cylinder, second magnetic cylinder, first coil, second coil, The first fixing piece, the second fixing piece and the temperature sensor; the protection tube is welded on the solid support body; after the first magnetic cylinder enters the first coil to a certain depth, it is respectively installed on the solid support body through the first fixing piece and the second fixing piece , and the first magnetic cylinder and the first coil are coaxially used together to form an exciter; the second magnetic cylinder enters the second coil to a certain depth and is respectively installed on the solid support body through the first fixing piece and the second fixing piece, and The second magnetic cylinder and the second coil are coaxially used together to form a detector; the exciter transmits the generated alternating force to the tuning fork through the solid support body, and the detector picks up the vibration frequency of the tuning fork to realize the vibration frequency of the tuning fork Detection; the vibration frequency of the tuning fork is a monotonous function relationship with the liquid density, which realizes the real-time online measurement of the liquid density; the temperature sensor is mounted on the solid support to detect the temperature of the measured liquid in real time, and is used to compensate the temperature of the tuning fork. Modulus of elasticity changes.

The tuning fork body and the solid support body are made of 316L stainless steel through finishing and integrated processing to form an "H"-shaped structure. Such a structure can make the system achieve a higher Q value and improve the stability and anti-interference ability of the system.

The protection tube is welded on the solid support body, and undercut grooves with a radius of 1 mm to 2 mm are respectively processed at a distance of 3 mm to 5 mm from the two end faces of the protection tube to eliminate the influence of stress on the vibration frequency of the tuning fork.

倍的线圈长度；所述第二磁缸进入第二线圈的深度为

倍的线圈长度。The depth at which the first magnetic cylinder enters the first coil is

times the length of the coil; the depth of the second magnetic cylinder entering the second coil is

times the coil length.

The principle of the present invention: according to the resonance principle of the sensitive element, when the tuning fork is in contact with the measured liquid, the additional mass of the tuning fork changes, resulting in a change in its vibration frequency, and the vibration frequency of the tuning fork and the liquid density are monotonous The functional relationship of the frequency changes to reflect the density of the measured liquid.

The advantage of the present invention compared with prior art is:

(1) The structure of the present invention realizes high measurement accuracy, good stability, high reliability, simple structure, small volume, low power consumption, and can continuously measure the density of various liquids at different temperatures online;

(2) The present invention uses the tuning fork body as the resonant element, and the tuning fork body adopts a peripheral fixed support structure, that is, the tuning fork body and the fixed support body are processed in one piece, forming an "H" type structure, which can make it reach a higher Q value, greatly improving the anti-interference ability, stable and reliable when working;

(3) The present invention adopts electromagnetic excitation and electromagnetic detection, the excitation and detection methods are simple, and the exciter and detector are small in size, simple in structure, and easy to install;

倍的线圈长度，这样检测出的信号较强，整个检测过程容易电路实现；在进行液体密度测量时，激励器和检测器与被测液体不相互接触，故不需要漏电保护；(4) magnetic cylinder of the present invention and coil are installed on the coaxial coaxial use on solid support body by fixture, form exciter and detector respectively; The depth that magnetic cylinder enters coil is

times the length of the coil, so that the detected signal is stronger, and the whole detection process is easy to realize the circuit; when the liquid density is measured, the actuator and the detector are not in contact with the measured liquid, so no leakage protection is required;

(5) The resonant tuning fork liquid density sensor for electromagnetic excitation detection of the present invention can be used for high-precision online continuous measurement of liquid density in industrial production, which is beneficial to realize automatic control in the production process.

Description of drawings

Fig. 1 is the structural assembly schematic diagram of the present invention;

Fig. 2 is a structural top view of the present invention;

Fig. 3 is a structural front view of the present invention;

Fig. 4 is the structural schematic diagram of tuning fork body, solid support body, magnetic cylinder, coil and fixing member of the present invention;

Fig. 5 is a schematic structural view of the tuning fork and the solid support of the present invention;

Fig. 6 is a schematic structural view of the protection tube of the present invention;

Fig. 7 is the structural representation of magnetic cylinder, coil and fixing part of the present invention;

Fig. 8 is a structural schematic diagram of the temperature sensor of the present invention.

Detailed ways

As shown in Figure 1, the resonance type tuning fork liquid density sensor of electromagnetic excitation detection of the present invention is made of tuning fork body 1, solid support body 2, protective tube 3, first magnetic cylinder 4, second magnetic cylinder 5, first coil 6 , the second coil 7, the first fixing part 8, the second fixing part 9 and the temperature sensor 10.

倍的线圈长度后分别通过第一固定件8和第二固定件9安装在固支体2上同轴配合使用组成激励器，第二磁缸5进入第二线圈7的深度为

倍的线圈长度后分别通过第一固定件8和第二固定件9安装在固支体2上同轴配合使用组成检测器。温度传感器10贴装在固支体2上。As shown in Figure 2, Figure 3, Figure 4, and Figure 7, the protective tube 3 is welded on the solid support body 2, and the radius is processed at a distance of 3mm to 5mm from the two end faces of the protective tube 3 (4mm in this embodiment). 1 mm to 2 mm undercut (1 mm in this embodiment), to eliminate the influence of stress on the vibration frequency of the tuning fork body 1 . The depth that the first magnetic cylinder 4 enters the first coil 6 is

times the length of the coil, respectively through the first fixture 8 and the second fixture 9 are installed on the solid support body 2 coaxially cooperate to form an exciter, the depth of the second magnetic cylinder 5 entering the second coil 7 is

times the length of the coil, they are installed on the solid support 2 through the first fixing part 8 and the second fixing part 9 respectively, and are coaxially used to form a detector. The temperature sensor 10 is mounted on the solid support 2 .

As shown in Figure 5, the structure of the tuning fork body 1 and the solid support body 2 is integrally processed to form an "H"-shaped structure. The tuning fork body 1 and the solid support body 2 are important parts of the sensor, and their production materials are made of 316L stainless steel, their processing quality directly affects the performance of the sensor, so it is processed by the method of finishing. This structure can make the system achieve a higher Q value and improve the stability and anti-interference ability of the system.

The working process of the present invention: the natural frequency of the tuning fork is measured in the air, a sinusoidal signal is generated by the circuit, the exciter vibrates at a frequency with a certain bandwidth and the generated alternating piezoelectric force is conducted to the The tuning fork makes the tuning fork generate simple harmonic vibration according to its own natural frequency, and then the detector obtains the vibration frequency of the tuning fork, and outputs the signal to the circuit, and then inputs it to the exciter, thus forming a closed loop In the excitation and vibration pickup system, since the tuning fork itself has the function of frequency selection, the tuning fork finally vibrates at its own natural frequency. When measuring the liquid density, when the tuning fork body is immersed in the measured liquid, since the actuator and the detector are not in contact with the liquid, the liquid will not affect the normal operation of the actuator and the detector. After the liquid is in full contact with the tuning fork, the additional mass of the tuning fork changes, and the natural frequency of the tuning fork vibration changes, and the vibration signal is obtained by the detector to detect the vibration frequency of the tuning fork. The vibration frequency of the tuning fork has a monotone function relationship with the liquid density, so the liquid density can be obtained.

Parts not described in detail in the present invention belong to the well-known technology in the art.

The present invention has been described in detail above through specific and preferred embodiments, but those skilled in the art should understand that the present invention is not limited to the above-described embodiments, and within the spirit and principles of the present invention, any Modifications, equivalent replacements, etc., should all be included within the protection scope of the present invention.

Claims (4)

1. the resonant mode tuning fork liquid density sensor that electric magnetization detects is characterized in that comprising: tuning fork body (1), solid support body (2), protection tube (3), the first magnetic cylinder (4), the second magnetic cylinder (5), first coil (6), second coil (7), first fixture (8), second fixture (9) and temperature sensor (10); Protection tube (3) is welded on the solid support body (2); The first magnetic cylinder (4) is installed on the solid support body (2) by first fixture (8) and second fixture (9) respectively after entering first coil (6) certain depth, and the first magnetic cylinder (4) and first coil (6) coaxial cooperation use composition driver; The second magnetic cylinder (5) enters in second coil (7) and is installed on the solid support body (2) by first fixture (8) and second fixture (9) respectively behind the certain depth, and the second magnetic cylinder (5) and second coil (7) coaxial cooperation use composition detecting device; Driver is transmitted to tuning fork body (1) with the alternating force that produces by solid support body (2), and detecting device picks up the detection of vibration frequency realization tuning fork body (1) vibration frequency of tuning fork body (1); The vibration frequency of tuning fork body (1) and fluid density are dull funtcional relationships, have realized the real-time online measuring of fluid density; Temperature sensor (10) is mounted on the solid support body (2), detects the fluid to be measured temperature in real time, is used for the elastic modulus change of compensation tuning fork body (1);

Described tuning fork body (1) and solid support body (2) adopt the 316L stainless steel to process through finishing is integrated, form " H " type structure.

2. the resonant mode tuning fork liquid density sensor that detects of electric magnetization according to claim 1; it is characterized in that: described protection tube (3) is welded on the solid support body (2); and process the relief groove that radius is 1mm～2mm at (3) two end face 3mm～5mm places of distance protection pipe respectively, to eliminate stress to the influence of tuning fork body (1) vibration frequency.

3. the resonant mode tuning fork liquid density sensor that detects of electric magnetization according to claim 1, it is characterized in that: the degree of depth that the described first magnetic cylinder (4) enters first coil (6) is

Loop length doubly.

4. the resonant mode tuning fork liquid density sensor that detects of electric magnetization according to claim 1, it is characterized in that: the degree of depth that the described second magnetic cylinder (5) enters second coil (7) is

Loop length doubly.

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