RU33221U1 - Ultrasonic device for measuring the liquid level in the tank - Google Patents

Description

The device relates to instrumentation, in particular, to ultrasonic level meters, and can be used to measure the level of liquid in tanks. Known ultrasonic devices for measuring the liquid level in the tank, containing an electro-acoustic transducer in contact with the outer surface of the tank, and an electronic unit for receiving and transmitting and processing information {1 + 3. A disadvantage of the known devices is the low accuracy. The disadvantage of the known devices are explained as follows. The level measurement in them is based on measuring the transit time in the medium of an ultrasonic pulse and the a priori embedded value of the speed of sound. Due to the fact that the speed of sound in liquids and gases depends on temperature, pressure, the presence of impurities, etc. 4 + 6, the use of known devices requires an a priori knowledge of the speed of sound in the working medium — the contents of the tank — with high accuracy and reliability, which is not always possible. The technical essence of the closest to the proposed is an ultrasonic device for measuring the liquid level in tanks, containing an electro-acoustic transducer in contact with the outer surface of the bottom of the tank, connected to the first input of the electronic

block transmit-receive and information processing, and the second electro-acoustic

a converter in contact with the side surface of the tank at a level known to be lower than the minimum liquid level in the tank at a known distance L from the opposite wall of the tank, connected to the second input of the electronic unit for transmitting and processing information 7.

The disadvantages of the known devices are limited scope and low accuracy.

The disadvantages of the known device are explained as follows.

The use of the known device is possible only in cases where it is possible to set the second electro-acoustic sensor on the side wall of the tank. In the event that the side wall of the tank is covered with thermal insulation, fittings, structural elements, etc. are installed on it, the installation of a second electro-acoustic sensor on the side wall is not possible.

Changes in the temperature of the working fluid, level of loading, wind load, deformation of the tank lead to a deviation of the true value of the measured base from the value of the measured base L in the calculation formula.

In addition, the installation of a second electro-acoustic transducer on the side wall of the tank allows you to determine the speed of sound in the working medium at the horizon on which it is located. However, due to a number of factors of compressibility of the working medium, the presence of temperature distribution, density distribution (especially when measuring suspensions and mechanical mixtures) - in reservoirs there is an unaccounted vertical distribution of sound velocity, different from that measured using the second electro-acoustic transducer.

The objective of the utility model is to eliminate these disadvantages.

The technical result is to increase the accuracy of measurements and expand the scope of the device.

To achieve the technical result, an ultrasonic device for measuring the liquid level in the tank containing the first electro-acoustic transducer in contact with the outer surface of the bottom of the tank, connected to the first input of the electronic unit for transmitting and processing information, the second electro-acoustic transducer connected to the second input of the electronic unit reception, transmission and processing of information, introduced new features: namely, the second electro-acoustic transducer t Also in contact with the outer surface of the bottom of the tank, while in the tank at level H, obviously lower than the minimum liquid level in it, a flat acoustic reflector is installed coaxially with the second electric transducer.

The best results are achieved if the level H satisfies the relation

;

A (1)

where h is the wall thickness of the tank;

Po is the density of the working fluid;

p is the density of the material of the tank wall.

and the diameter of the flat acoustic reflector D, the diameter of the electro-acoustic transducers d, the distance between the centers of the first and second electro-acoustic transducers 1, and the installation level of the flat acoustic reflector H satisfy the relations: d t „59 ° I D w-b-ig + t (2) arctg where I am the sound wavelength in the liquid. and flatness (angle between the plane of the acoustic reflector and the tank) and satisfies the ratio a arcsin. Achieving a positive result is explained by the fact that the installation of a flat acoustic reflector (reference platform) in the working medium is coaxial with the second electro-acoustic transducer in contact with the bottom of the tank at a distance of H provides measurement of the speed of sound in a working environment, taking into account its vertical distribution. Condition (1) I, in accordance with the results of work 8, ensures a decrease in the level of free vibrations in the mechanical system of the tank wall, the working medium that occurs after the end of the pulse and prevents the detection of a pulse reflected from the interface by 40 dB. Condition (2), taking into account the fact that the width of the main lobe of the directivity characteristics of the electro-acoustic transducer is 9 D 59 ° I 2N d (3) 2N (4)

where I am the wavelength in the working medium.

ensures that the reflector is located outside the main lobe of the directivity characteristics of the first electro-acoustic transducer.

Condition (3), taking into account (5), ensures that the main lobe of the directivity of the second electro-acoustic transducer completely hits the reflector located coaxially with it in the working medium.

Condition (4) ensures, when a is non-flat, that the acoustic beam reflected from the extreme points of the reflector hit the working surface of the second electro-acoustic transducer.

. Figure 1 shows a block diagram of the proposed device. An ultrasonic device for measuring the liquid level in the tank contains the first and second electro-acoustic transducers 1 and 2, for example, described in 10, in contact with the outer surface of the bottom of the tank 3, connected respectively to the first and second inputs of the electronic unit for transmitting and processing information, for example, described in 11, and a flat acoustic reflector 5 located in the liquid b coaxially with the second electro-acoustic transducer 2 at a calibrated level H, while the diameter of the flat reflector D, diameter of the first and second electroacoustic

transducers d, distance H, the distance between the centers of the transducers L and the non-flatness of the reflector relative to the bottom of the tank a are related by the relations

d „59 ° I D .tg- + D 59 ° I

arctg

2H d

а, arcsin - 2Я and the distance of the reference site Н, the wall thickness of the tank h and

the density of the wall of the tank p and the working fluid po are related by the relation

, 36-hp

The operation of the device is as follows. When it is turned on, the transmit-receive and information processing unit 4 generates an electrical signal of a given frequency f / (which corresponds to wavelength A in the liquid), which is supplied to the first and second electro-acoustic transducers 1 and 2 in contact with the outer surface of the bottom of the tank 3, and transforming an electric impulse into acoustic vibrations. The latter pass through the wall of the tank 3 into liquid 6. The pulses emitted by the first electro-acoustic transducer 1 pass through the liquid 6, reach the desired interface 7, are reflected from it, come to the bottom of the tank 3, pass through it and are received by the first electro-acoustic transducer 1. The pulses emitted by the second electro-acoustic transducer 2 pass through the liquid 6, are reflected from the flat acoustic reflector 5 and are received by the second electro-acoustic transducer 2. Electroacoustic RP G converters 1 and 2 convert acoustic signals into electrical signals which are respectively supplied to first and second inputs of the electronic unit receiving the transmission and processing of information 4, wherein the processing the received signals is produced and calculating the liquid level in the tank nJ, from the formula:

I

where ti and fe, respectively, the time intervals between the moments of radiation and reception of reflected pulses by the first and second electro-acoustic transducers, respectively.

6

The presence of a flat acoustic reflector - a reference platform allows us to solve the technical problem, namely, to expand the scope and increase the accuracy of measuring the liquid level in the tank and at different ratios.

Claims (3)

1. An ultrasonic device for measuring the liquid level in the tank, containing a first electro-acoustic transducer in contact with the outer surface of the bottom of the tank, connected to the first input of the electronic unit for transmitting and processing information, a second electro-acoustic transducer connected to the second input of the electronic receiving-transmitting unit, and information processing, characterized in that the second electro-acoustic transducer also contacts the outer surface of the bottom of the tank, p and in this tank at the level H, certainly below the minimum liquid level therein coaxially mounted second electrical converter planar acoustic reflector. 2. The ultrasonic device according to claim 1, characterized in that the level of installation of a flat acoustic reflector H satisfies the ratio

where h is the wall thickness of the tank; ρ ₀ is the density of the liquid in the tank; ρ is the density of the material of the wall of the tank. 2. The ultrasonic device according to claim 1, characterized in that the level of installation of a flat reflector H, the diameter of the reflector D, the diameter of the electroacoustic transducers d, the distance between the centers of the first and second electroacoustic transducers L and the non-flatness of the installation of a flat acoustic reflector α satisfy the relations: