Sonar ranging principle
Sonar echo ranging technology has a history of 100 years. In 1906, it was invented by the British Navy's Lewis Nixon and applied to submarines for the first time. This technology uses underwater acoustic reflection to detect, range, and locate underwater targets. It is the most reliable, most widely used, and most important technology in underwater acoustics. The sonar external level gauge is based on the sonar echo ranging technology to achieve the internal level measurement outside the tank, thereby achieving a "completely non-contact" external level measurement. The sonar ranging principle is the basis of the external level measurement of the external level gauge. This theoretical basis is reliable.
How to implement the theory?
The liquid level measuring head attached to the bottom of the storage tank emits a certain frequency of ultrasonic waves. The ultrasonic wave penetrates the bottom tank wall and propagates in the liquid medium in the tank, reaches the liquid surface, forms an echo signal, and the echo signal reaches the bottom of the tank. , Penetrates the bottom tank wall again, the same echo signal is received by the same liquid level measuring head, and transmitted back to the host. The host analyzes the time from the transmission of the ultrasonic wave to the formation of the echo signal, according to the formula height (H) = speed ( S) × time (T) calculation, the liquid level is obtained. among them
Height (H): height of liquid level;
Speed (S): The propagation speed of sound waves in a liquid medium, the propagation speed of sound waves in different media is different;
Time (T): The time when the acoustic wave forms an echo in the liquid, which is obtained by the host computer by analyzing the echo signal received by the liquid level measuring head.
2. "Micro-vibration analysis" technology (patent certificate number 1594973)
"Micro-vibration analysis technology" is a patented technology for sonic signal processing due to the external measurement of liquid level. This acoustic signal processing technology is based on the application experience of Xi'an Dinghua Electronic external measuring level gauge in nearly a thousand users around the world. Through nearly 10,000 sets of external measuring level gauges, they are actually used in hundreds of operating conditions. Accumulated field data for more than two decades, in-depth summary and knowledge and experience, forming advanced judgment methods and algorithms.
"Micro-vibration analysis" technology is the guarantee of stable measurement and reliable operation of the sonar external level gauge.
Due to the complicated working conditions of some containers, for example:
1. The degree of impurity deposition in the container and the different physical characteristics of the medium;
2. The speed of feeding and discharging is too fast, causing a strong impact, and the liquid level in the container will form a sharp fluctuation;
3. The medium is highly volatile, and the liquid surface forms a vapor and liquid mixture.
Will cause not only the liquid level echo signal received by the liquid level measuring head, but also some other interference signals, which will interfere with the instrument to determine the time when the sound wave reflects from the liquid level and forms an echo; the sound wave signal will have Significant attenuation; the propagation speed is different in different liquid media, and the propagation speed will change when the temperature and density of the liquid medium change, which will affect the accurate measurement of the liquid level.
"Micro-vibration analysis technology" through intelligent processing methods and advanced echo recognition algorithms, overcome these recognized problems in the field of liquid level measurement. Its learning characteristics can identify and reject interference signals such as container wall aftershocks, multiple echoes, and false echoes. Ensures effective tracking and monitoring of echo signals returning from the liquid surface.
3.Automatic calibration technology
"Auto-calibration technology" is a patented technology, which guarantees the accurate measurement of the sonar external test level gauge. When the temperature of the same liquid medium changes greatly, and the liquid composition and density change greatly, it will affect the acoustic waves in the liquid.
The propagation speed will have a greater impact, which will cause measurement errors. In order to ensure the measurement accuracy of the instrument, a calibrator can be installed in the container and a liquid level measuring head (calibration measuring head) for calibration can be used to calibrate the measurement. The head measures the standard length of the liquid column in the calibrator. The standard length is 1m. Since the calibration head and the level measuring head work in the same way (the working principle of sonar echo ranging), the speed (S0) = distance (H0 ) / Time (T0) to get the ultrasound during calibration
The speed of propagation in the liquid in the device. among them:
Speed (S0): Real-time sound wave propagation speed;
Distance (H0): height of liquid level in the calibrator;
Time (T0): The echo time of the liquid surface in the calibrator.
Because the liquid in the calibrator is in communication with the liquid in the container, the temperature and composition of the liquid in the calibrator are the same as the liquid in the container, and the propagation speed of the sound waves is the same. , S0 = S, bring the meter to calculate the liquid level formula: height (H) = speed (S) × time (T) to calculate the liquid level. The meter will automatically select the corrected sound wave propagation speed for calculation and automatically calibrate it every 15 minutes, so that the measured liquid level is excluded from the influence of liquid temperature and composition changes.
The principle of automatic calibration is to find a known length on the container that will fill the liquid medium in the container, and self-calibrate the propagation speed to ensure high-precision measurement under any conditions. If the container is unconditionally installed with a calibrator, the container's known diameter can be used as an calibrator to achieve automatic calibration.
4. Technical advantages
From 1997 to 2007, the technical problems recognized in the field of external level measurement were solved, and the following factors interfered with the level measurement.
A. Aftershocks of the container wall; B. Multiple echoes; C. False echoes; D. The significant attenuation of the acoustic signal when it penetrates the container wall; E. The effect of changes in the composition of the medium on the sound velocity
Ensure A, stable and reliable performance; B, accurate results; C, intelligent measurement. Enables external level gauges to handle a variety of complex field conditions
Sonar type external level gauge
1. Applicable to harsh working conditions: ultra-high pressure vessels, high-purity media, ELL series instrument functions are not affected by temperature and pressure, and reliable measurement under complex working conditions. Isolated measuring level gauge for "dangerous chemicals" such as highly toxic, corrosives, strong acids and strong bases;
2. For open storage tanks and atmospheric pressure vessels, external level gauges can reliably perform level measurement without being affected by the surface conditions of complex liquid media;
3. Easy installation and maintenance: ELL series meters can be installed and maintained online without cleaning tanks, moving fire, or opening holes;
4. There is no mechanical moving part in the measuring head and the instrument, and it is strictly sealed, isolated from the outside, will not wear or corrode, and is very durable and reliable;
5. Safety and environmental protection: no holes, no flanges, no increase in leakage points; no fire, no explosion danger.