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What Is The Difference Between Radar Level Sensor And An Ultrasonic Level Sensor?

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What is the difference between radar level sensor and an ultrasonic level sensor? What are the two measuring principles? What are the operating conditions for a radar level sensor and an ultrasonic level sensor? A radar level sensor and an ultrasonic level sensor What is the measurement accuracy of the level sensor? Let us explain these two level sensors on these issues.


The radar level sensor adopts the transmission-reflection-reception working mode. The radar level sensor antenna emits electromagnetic waves. These waves are reflected by the surface of the measured object and then received by the antenna. The time from when the electromagnetic wave is transmitted to when it is received is proportional to the distance to the liquid surface. The relationship is as follows:

  D = CT / 2

  D in the formula-the distance from the radar level sensor to the liquid surface

  C——speed of light

  T——Electromagnetic wave running time


The radar level sensor records the elapsed time of the pulse wave, and the transmission speed of the electromagnetic wave is constant, 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 methods of radar level sensor, namely FM continuous wave type and pulse wave type. Liquid level sensors using FM continuous wave technology have large power consumption and must adopt a four-wire system. The electronic circuit is complicated. The level sensor using radar pulse wave technology has low power consumption and can be powered by two-wire 24VDC, which is easy to achieve intrinsic safety and has a wider range of applications.


Ultrasonic uses sound waves, and radar uses electromagnetic waves. This is the biggest difference. Moreover, the penetration and directivity of ultrasonic waves are much stronger than electromagnetic waves, which is why ultrasonic detection is now more popular.

  Differences in main applications:

  1. Ultrasonic accuracy is not as good as radar.

  2. Relative price of radar is high.

  3. When using radar, consider the dielectric constant of the medium.

  4. Ultrasound cannot be used in vacuum, high steam content or foam on the liquid surface.

  5. Radar measurement range is much larger than ultrasonic.

  6. Radar has horn type, rod type and cable type. Relative ultrasonic waves can be applied to more complicated working conditions.


We generally call sound waves with an acoustic wave frequency exceeding 20kHz as ultrasonic waves. Ultrasonic waves are a type of mechanical waves, that is, a process of mechanical vibration propagation in elastic media. It is characterized by high frequency, short wavelength, and small diffraction phenomenon. It has good directivity and can be directional and propagated as rays. Ultrasonic waves have very low attenuation in liquids and solids, and therefore have strong penetrating power. Especially in solids that are opaque to light, ultrasonic waves can penetrate tens of meters in length, and there will be significant reflection when they encounter impurities or interfaces. Ultrasonic measurement Level is the use of this feature.


In the ultrasonic detection technology, no matter what kind of ultrasonic instrument, it is necessary to transmit the electric energy converted ultrasonic wave, and then receive it back and convert it into electrical signals. The device that accomplishes this function is called an ultrasonic transducer, also called a probe. As shown in the figure, the ultrasonic transducer is placed above the measured liquid, and the ultrasonic wave is transmitted downward. The ultrasonic wave passes through the air medium, is reflected back when it encounters the water surface, and is received by the transducer and converted into an electrical signal. The electronic detection part detects this signal and turns it into a liquid level signal for display and output.


According to the principle of ultrasonic wave propagation in a medium, if the conditions of medium pressure, temperature, density, and humidity are constant, the propagation speed of the ultrasonic wave in the medium is a constant. Therefore, when the time required for the ultrasonic wave to be received from the reflection of the liquid surface is measured, the distance through which the ultrasonic wave passes can be converted, and the liquid level data is obtained.


Ultrasound has a dead zone. The distance between the sensor installation position and the measurement liquid must be calculated during installation.