Differences between ultrasonic level gauges and radar level gauges

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1. The principles are different: ultrasonic level gauges use sound waves, while radar level gauges use electromagnetic waves. Ultrasonic level gauge: When an ultrasonic level gauge is in operation, high-frequency pulsed sound waves are emitted by the transducer (probe). These waves are reflected upon hitting the surface of the object being measured (the water surface). The reflected waves are then received by the same transducer (probe) and converted into electrical signals. The time between pulse transmission and reception (the time it takes for the sound wave to travel) is proportional to the distance from the transducer to the object’s surface. The distance S that the sound wave travels can be expressed using the formula: S = C × T / 2. When installing an ultrasonic level gauge, it is necessary to take into account its blind zone. Once the liquid level reaches the blind zone, the ultrasonic transmitter can no longer measure it; therefore, when determining the range of the ultrasonic level gauge, a margin of 50 centimeters must be reserved. During installation, the probe of the transmitter must be positioned about 50 centimeters above the highest possible liquid level. This ensures accurate level monitoring as well as the safety of the ultrasonic level gauge. Ultrasonic level gauges use sound waves, while radars use electromagnetic waves; this is the biggest difference between the two. Since ultrasonic waves have much stronger penetration and directivity than electromagnetic waves, the basic working principle of a radar level gauge is emission-reflection-reception. The antenna of the radar sensor emits electromagnetic wave signals in the form of beams; the emitted waves are reflected by the surface of the material being measured, and the reflected echo signals are once again received by the antenna. Each point in the transmitted and reflected beams is acquired using ultrasonic sampling. The signal is processed by an intelligent processor to determine the distance between the medium and the probe; this value is then displayed on a terminal monitor for purposes such as alerting and operation control. 2. Different medium temperatures and pressures: Ultrasonic level gauges can only be used in containers at atmospheric pressure, and the temperature at the probe site must not exceed 80°C, as the speed of sound is greatly affected by temperature and pressure. Radar level gauges use electromagnetic waves, are not affected by vacuum, and have a wide range of applicability in terms of medium temperature and pressure. Click to view--Summary of Chemical Engineering Skill Training Courses in 2023 3. Different application scenarios 　　Due to the different measurement principles of ultrasound and radar, their application scenarios also vary. Radar level gauges use electromagnetic waves, which are affected by the dielectric constant of the substance being measured, whereas ultrasonic waves are mechanical waves that are influenced by the density of the medium in question. Therefore, when measuring materials with very low dielectric constants, the performance of radar level gauges is significantly reduced, making them unsuitable for such measurements. The measurement range of radar level gauges is much larger than that of ultrasonic level gauges. Radar emits electromagnetic waves, allowing measurements to be taken without the need for a medium of propagation. Ultrasonic waves, on the other hand, are sound waves and mechanical waves that require a medium for propagation. Therefore, ultrasonic level gauges cannot be used in conditions such as vacuum, high steam content, or liquid surfaces with foam. 4. Ultrasonic level gauges have temperature limitations; generally, the temperature at the probe should not exceed 80 degrees, and the speed of sound is greatly affected by temperature. Ultrasonic level gauges are highly sensitive to pressure; generally, a pressure level of 0.3 MPa or less is required, as sound waves are generated through vibration, and high pressure can affect the components responsible for producing sound. When there is a lot of fog or dust in the measurement environment, ultrasonic level gauges cannot perform accurate measurements either. 　　In contrast, radar uses electromagnetic waves, is not affected by vacuum, and has a wide range of applicability across different temperatures and pressures of the medium; with the advent of high-frequency radar, its applications have become even broader, while ultrasonic level gauges are subject to many more limitations. 5. The components used for generating the two types of waves are different; ultrasonic waves are generated through the vibration of piezoelectric materials, which is why ultrasonic level gauges cannot be used in environments with high pressure or negative pressure, and are generally only applicable to containers at normal pressure. Radar level gauges, on the other hand, can be used in high-pressure process tanks. 6. Different precision: Radar level gauges have higher precision than ultrasonic level gauges. However, whether it is a radar level gauge or an ultrasonic level gauge, when installed on a tank, it should not be placed at the feed inlet nor near a ladder; it should be kept 300 to 500 mm away from the tank wall to avoid interference from echoes. In situations with stirring and large surface fluctuations, an appropriate installation method must also be chosen. The transmission angle of radar is greater than that of ultrasonic waves; therefore, contactless radar is not recommended for small or elongated containers, with guided-wave radar being the preferred option in such cases. Finally, there are the issues related to precision. Of course, the precision of radar is definitely higher than that of ultrasonic sensors; high-precision radar is used in storage tanks, rather than ultrasonic sensors. 7. Radar level gauges come in horn type, rod type, and cable type, and can be used in various measurement scenarios; therefore, compared to ultrasonic level gauges, radar level gauges can be applied to more complex conditions. 8. In terms of price, radar level gauges are relatively more expensive compared to ultrasonic level gauges. Of course, some ultrasonic sensors with a large measurement range also come at a high price; for ranges of 6 to 70 meters, even radar level gauges with very large ranges are not sufficient, and in such cases ultrasonic level gauges are the only option.