Difference Between Radar Level Gauge And Ultrasonic Level Gauge

The radar level gauge adopts the working mode of transmission-reflection-reception. The antenna of the radar level gauge emits electromagnetic waves. These waves are reflected by the surface of the measured object and then received by the antenna. The time from emission to reception of electromagnetic waves is proportional to the distance to the liquid surface. The relationship is as follows:
D=CT/2
In the formula, D——the distance from the radar level gauge to the liquid surface
C - the speed of light
T——electromagnetic wave running time
The radar level gauge records the elapsed time of the pulse wave, and the transmission speed of the electromagnetic wave is constant, so the distance from the liquid surface to the radar antenna can be calculated, so as to know the liquid level of the liquid surface.
In practical application, there are two types of radar level gauges, FM continuous wave type and pulse wave type. The liquid level gauge using frequency modulation continuous wave technology consumes a lot of power, must use a four-wire system, and has complex electronic circuits. The liquid level gauge using radar pulse wave technology has low power consumption and can be powered by two-wire 24VDC, which is easy to achieve intrinsic safety, high accuracy, and wider application range.
Ultrasound uses sound waves, while radar uses electromagnetic waves. This is the biggest difference. Moreover, the penetration and directionality of ultrasonic waves are much stronger than electromagnetic waves, which is why ultrasonic detection is more popular now.
Differences in main application occasions:
1. Ultrasonic accuracy is not as good as radar.
2. Radar is relatively expensive.
3. When using radar, the dielectric constant of the medium should be considered.
4. Ultrasonic waves cannot be used in working conditions such as vacuum, high steam content or foam on the liquid surface.
5. The radar measurement range is much larger than that of ultrasonic waves.
6. Radar has horn type, rod type, and cable type, which can be applied to more complicated working conditions than ultrasonic waves.
We generally refer to sound waves with a sound wave frequency exceeding 20kHz as ultrasonic waves. Ultrasonic waves are a type of mechanical wave, that is, a propagation process of mechanical vibration in elastic media. It is characterized by high frequency, short wavelength, and small diffraction phenomenon. Good directionality, can become ray and directional propagation. The attenuation of ultrasonic waves in liquids and solids is very small, so the penetrating ability is strong, especially in solids that are opaque to light, ultrasonic waves can penetrate tens of meters in length, and there will be significant reflection when encountering impurities or interfaces. The material level is to use this characteristic of it.
In ultrasonic testing technology, no matter what kind of ultrasonic equipment, it is necessary to convert electrical energy into ultrasonic waves, and then receive them back and transform them into electrical signals. The device that completes this function is called an ultrasonic transducer, also known as a probe. As shown in the figure, the ultrasonic transducer is placed above the liquid to be measured, and the ultrasonic wave is emitted downward. The ultrasonic wave passes through the air medium and is reflected back when it encounters the water surface, and is received by the transducer and converted into an electrical signal. After detecting this signal, the electronic detection part turns it into a liquid level signal for display and output.
According to the principle of ultrasonic propagation in the medium, if the medium pressure, temperature, density, humidity and other conditions are constant, the propagation speed of ultrasonic waves in the medium is a constant. Therefore, when the time required for the ultrasonic wave to be reflected from the liquid surface to be received is measured, the distance traveled by the ultrasonic wave can be converted, that is, the liquid level data can be obtained.
Ultrasonic has a blind area, and the distance between the installation position of the sensor and the liquid to be measured must be calculated during installation.