Level is one of the important target parameters of industrial process monitoring. In the continuous level measurement of various tanks, silos, pools, etc., it is difficult to have level instruments that can meet all working conditions because of the wide variety of field conditions.
Among them, radar and ultrasonic level gauges are widely used in non-contact measuring instruments. So, what is the difference between radar level meter and ultrasonic level meter? What is the principle of these two kinds of measurement? What are the advantages of radar level meter and ultrasonic level meter?
First, ultrasonic level meter
We generally call the sound wave with a frequency of more than 20kHz ultrasonic wave, ultrasonic wave is a kind of mechanical wave, that is, mechanical vibration in the elastic medium in a propagation process, it is characterized by high frequency, short wavelength, small diffraction phenomenon, and good directivity, can become a ray and directional propagation.
Ultrasonic attenuation in liquids and solids is very small, so the penetration ability is strong, especially in the light opaque solids, ultrasonic can penetrate tens of meters in length, encounter impurities or interfaces will have significant reflection, ultrasonic level measurement is the use of its this feature.
In ultrasonic detection technology, no matter what kind of ultrasonic instrument, it is necessary to convert electrical energy into ultrasonic emission, and then receive back into electrical signals, the device to complete this function is called ultrasonic transducer, also known as the probe.
When working, the ultrasonic transducer is placed above the measured object and emits ultrasonic wave downward. The ultrasonic wave passes through the air medium, is reflected back when it meets the surface of the measured object, and is received by the transducer and converted into an electrical signal. After detecting this signal, the electronic detection part turns it into a level signal for display and output.
Two, radar level meter
The operating mode of the radar level meter is the same as that of the ultrasonic level meter, and the radar level meter also uses the transmitting – reflecting – receiving working mode. The difference is that the measurement of the radar ultrasonic level meter mainly relies on the ultrasonic transducer, while the radar level meter relies on the high-frequency head and the antenna.
Ultrasonic level meters use mechanical waves, while radar level meters use ultra-high frequencies (several G to tens of G Hertz) electromagnetic waves. Electromagnetic waves travel at the speed of light, and the travel time can be converted into a level signal by electronic components.
Another common radar level meter is a guided wave radar level meter.
Guided wave radar level meter is a radar level meter based on the time domain reflectometry (TDR) principle. The electromagnetic pulse of the radar level meter propagates along the steel cable or probe at the speed of light. When it encounters the surface of the measured medium, part of the pulse of the radar level meter is reflected to form an echo and returns to the pulse launching device along the same path. The distance between the transmitter and the measured medium surface is proportional to the propagation time of the pulse during which the liquid level height is calculated.
Third, the advantages and disadvantages of radar and ultrasonic level meter
1. Ultrasonic accuracy is not as good as radar;
2. Due to the relationship between frequency and antenna size, the radar level meter with higher frequency is smaller and easier to install;
3. Because the radar frequency is higher, the wavelength is shorter, and there is better reflection on tilted solid surfaces;
4. Radar measurement blind area is smaller than ultrasonic;
5. Due to the higher radar frequency, the radar beam Angle is small, the energy is concentrated, and the echo ability is enhanced while it is conducive to avoiding interference;
6. Compared with ultrasonic level meters using mechanical waves, radar is basically not affected by vacuum, water vapor in the air, dust (except graphite, ferroalloy and other high dielectric dust), temperature and pressure changes;
Post time: Sep-18-2023