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It is a kind of mechanical wave, which is the propagation process of mechanical vibration in the medium. When the vibration frequency is more than ten Hz to 10,000 Hz, it can cause human hearing, called sound wave; lower frequency mechanical wave is called infrasound wave; mechanical wave above 20 kHz It is called ultrasonic wave, and ultrasonic detection is generally used for level detection. Sound waves can travel in gases, liquids, solids, and have a certain speed of propagation. The sound waves are absorbed and attenuated as they pass through the medium. The gas absorption is most strongly attenuated, the liquid is second, and the solid absorption is minimized. When the sound waves pass through the interface of different media, reflection will occur. The strength of the reflected wave is determined by the acoustic impedance of the medium on both sides of the interface. The greater the difference between the acoustic resistance of the two media, the stronger the reflected wave. The acoustic impedance is the product of the density of the medium and the speed of sound. When sound waves propagate from liquid or solid to gas, or vice versa, sound waves are almost completely reflected due to the disparity in the acoustic resistance of the two media. The directionality of the sound wave propagates with the increase of the frequency of the sound wave, and the sound speed of the sound is sharper. The ultrasonic wave can be approximated as a straight line and has good directivity. The measurement of the level can be performed based on the relationship between the time interval from the emission of the sound wave to the reception of the reflected echo and the height of the level.
The measuring principle of ultrasonic level gauge:
Ultrasonic liquid level gauge uses the principle of ultrasonic wave reflection at the liquid level to detect the liquid level, that is, the principle of echo distance measurement is applied, as shown in the figure. When the ultrasonic probe emits a short ultrasonic pulse to the liquid surface, after a time t, the probe receives an echo pulse reflected from the liquid surface. Therefore, the distance h from the probe to the liquid surface can be obtained by the following formula: the distance from the ultrasonic probe to the bottom of the container is h, and the liquid level value is
H=h-0.5vt
Where v is the propagation velocity (referred to as the speed of sound) (m/s) of the ultrasonic wave in the measured medium.
It can be seen that by knowing the sound velocity v, the liquid level height can be obtained by accurately measuring the time t. Of course, the precondition is that the speed of sound v must be constant, or some way to compensate for changes in the speed of sound.
One of the problems in the specific use of ultrasonic level gauges is how to determine the emission energy of the ultrasonic waves. If the emission energy is increased, the propagation distance of the acoustic wave in the medium can be increased, which is suitable for large level detection, and the energy of the receiver is higher, and the precision is improved. However, this will also have an adverse effect on the measurement. For liquid measurement, high emission energy will produce an unfavorable ultrasonic effect, resulting in the formation of a large number of cavitation bubbles in the liquid, so that the ultrasonic energy is consumed in this area and cannot be transmitted farther. At the same time, and the sound energy is absorbed by the medium, the temperature of the medium is increased, the characteristics of the medium are changed, and the measurement accuracy is lowered. Therefore, the higher frequency ultrasonic pulse is usually used, which reduces the energy of the ultrasonic wave emitted per unit time and increases the amplitude of the ultrasonic pulse.
New ultrasonic level gauge JZ-MA
I. Overview
The ultrasonic level meter is a well-known person who has absorbed the advantages of various level instruments at home and abroad. The universal level meter with full digital and humanized design concept has perfect level measurement and control, data transmission and human-computer communication. This product adopts modular circuit design, military quality multi-layer PCB board, compact hardware structure and reasonable layout. It can also add modules according to customer needs to realize other functions, RS-485 module, current output module, which can better match PLC and other control instruments.
This product uses imported industrial grade chips, digital temperature compensation, etc... related ASICs. It has strong anti-interference ability, can set arbitrarily upper and lower limit nodes and online output adjustment, and has on-site display. The outer casing is made of engineering plastic ABS waterproof casing, and the casing is compact and quite sturdy. This product can meet most liquid level and material level measurement requirements without touching industrial media. It completely solves the defects of winding, clogging, leakage, medium corrosion and inconvenience caused by traditional measuring methods such as pressure type, capacitance type and float type. . Therefore, it can be widely used in various fields related to material level and liquid level measurement and control.
Second, product features
â— Wide voltage adaptability range, can work in DC voltage of 12-24V.
â— Backup and restore settings
â—Measure multiple physical functions
â—The analog output function can be adjusted arbitrarily
â—With full scale start and end point arbitrary setting function
â—With digital filtering and echo recognition
â— Manually set fixed interference filtering function
â— Support custom serial data format
â— With value-added/difference ranging selection, both distance and level can be measured.
â— With 1-15 emission pulse intensity, it can be set according to working conditions.
The following items are ordered when ordering
â— 3-way limit NPN open collector control output setting for material level and liquid level control.
â— 2-way relay control output setting for material level and liquid level control.
â— 4 ~ 20mA current output, RS485 serial data output or 0 ~ 5V voltage and other analog output optional.
â— Select PC serial port output and conversion accessories, which can be directly connected to the PC unit network.
Third, the main technical parameters
Range: 5, 8, 10, 12, 15m (optional when ordering)
Blind zone: <0.4-0.5m (different from range)
Error: 0.25% FS
Display: four eight-segment 0.36-inch LED (optional LCD)
Minimum display resolution: 1mm
Keyboard: three-touch button
Operating frequency: 20 ~ 350KHz (depending on model specifications)
Optional power supply: 12-24VDC or 220VAC
Power consumption: <1.5W
Optional output mode: 4~20mA RL>600Ω (standard)
1~5V\1~10V
RS485 (optional Bluetooth conversion accessory)
3-way NPN (configurable as PP pulse output)
2-way relay (AC: 5A 250V DC: 10A 24V)
Instrument material: ABS engineering plastic
Dimensions: Φ92mm × 198mm × M60
Electrical interface: M20X1.5 (two groups)
Mounting interface: M60X2 or ¢61MM round hole (with large nut)
Incoming cable: internal terminal block user-defined
Working environment: normal temperature, normal pressure
Protection level: IP65 (can be customized with higher protection level)
Explosion-proof grade: EXia IIBT4Gb (order purchase)
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