The difference Between Ultrasonic Level Gauge and Radar Level Gauge

What is the difference between an ultrasonic level gauge and a radar level gauge? 

Ultrasonic level gauges and radar level gauges are both liquid level measuring instruments. As the name suggests, one uses ultrasonic waves and the other uses electromagnetic waves. Besides, what are the differences between ultrasonic level gauges and radar level gauges?

Different principle

1. Ultrasonic level gauge, ultrasonic level gauge is a digital level instrument controlled by a microprocessor. In the measurement, the pulsed ultrasonic wave is sent out by the sensor (transducer), and the sound wave is received by the same sensor after being reflected by the surface of the object, and converted into an electrical signal. And calculate the distance from the sensor to the measured object from the time between the emission and reception of the sound wave. Due to the non-contact measurement, the measured medium is almost unlimited, and it can be widely used for the height measurement of various liquid and solid materials. The ultrasonic level gauge uses sound waves, and the radar uses electromagnetic waves. This is the biggest difference between the two. Since the penetration ability and directionality of ultrasonic waves are much stronger than electromagnetic waves, this is also the reason why ultrasonic detection is more popular at present.

2. Radar level gauge, the radar level gauge adopts the circuit design of high frequency microstrip line structure, and the internal circuit generates microwave pulse signal. Based on the design principle of high-frequency waveguides, microwave pulses are emitted from the end of the antenna through a PTFE emitter. When the transmitted pulse hits the surface of the measured medium, part of the energy is reflected back and received by the same antenna. Through the principle of time expansion technology, the time interval between the transmitted pulse and the received pulse is calculated, so as to further calculate the distance from the antenna to the surface of the measured medium.

Different application scenarios

Due to the different measurement principles of ultrasonic and radar, their applications are also different.

1. The radar level gauge uses electromagnetic waves, which are affected by the dielectric constant of the measured material, while ultrasonic waves are mechanical waves, which are affected by the density of the measured medium. Therefore, when measuring substances with very low dielectric constants, the measurement effect of the radar level gauge will be greatly reduced, and it is not suitable to use the radar level gauge for measurement.

2. The measuring range of the radar level gauge is much larger than that of the ultrasonic level gauge. Radar emits electromagnetic waves that can be measured without the aid of a propagation medium. Ultrasound is a sound wave and a mechanical wave, which needs to be transmitted by means of a transmission medium. Therefore, the ultrasonic level gauge cannot be used in vacuum, high steam content or foam on the liquid surface.

3. The ultrasonic level gauge has a temperature limit. Generally, the temperature at the probe cannot exceed 80 degrees, and the speed of the sound wave is greatly affected by the temperature. The ultrasonic level gauge is greatly affected by the pressure, and generally requires less than 0.3MPa, because the sound wave is emitted by vibration, and the sound-emitting parts will be affected when the pressure is too high. When there is a lot of fog or dust in the measurement environment, the ultrasonic level gauge cannot measure well.

4. In contrast, radar uses electromagnetic waves, which are not affected by vacuum, and has a wide range of application to medium temperature and pressure. With the emergence of high-frequency radar, its application range is more extensive. more limited.

5. The radar level gauge has horn type, rod type and cable type, which can be applied to different measurement conditions. Therefore, compared with the ultrasonic level gauge, the radar level gauge can be applied to more complex working conditions.

Wave elements emit differently

For example, ultrasonic waves are emitted by the vibration of piezoelectric substances, so ultrasonic level gauges cannot be used in situations with high pressure or negative pressure, and are generally only used in atmospheric pressure vessels. The radar level gauge can be used in high pressure process tanks. The launch angle of radar is larger than that of ultrasonic waves. Non-contact radar is not recommended for small containers or slender containers. Guided wave radar is generally recommended. The last is the question of accuracy. Of course, the accuracy of radar must be higher than that of ultrasonic, and high-precision radar must be used on the storage tank, instead of ultrasonic.

In terms of price, compared with the ultrasonic level gauge, the price of the radar level gauge is relatively high. Of course, the price of some large-scale ultrasonic waves is not low, such as the range of 6~70 meters, which cannot be achieved by radar level gauges with large ranges, and only ultrasonic level gauges can be selected. However, whether it is a radar level gauge or an ultrasonic level gauge, attention must be paid to the installation location and blind spot during the installation process. For example, when it is installed on the tank body, it should not be installed at the feed inlet, and should not be installed near the ladder, and the distance from the tank wall should be 300 to 500 mm to prevent echo interference. In the occasions where there is stirring and the liquid level fluctuates greatly, an appropriate installation method should also be selected.