Advantages and limitations of radar level gauges
High-frequency radar level meter (mainly refers to 26GHz and 24GHz) has high energy and small beam angle (usually uses a horn antenna of Φ95 with a beam angle of 8o, while 6GHz low-frequency pulse radar uses a horn antenna with a diameter of 24GHz and a beam angle of 15o) , the antenna size is small and the precision is high.
The bulk material positions of 50mm and 50mm were measured at two wavelengths of 26GHz and 6GHz, respectively. When measuring the bulk material position, it was mainly through the diffuse reflection of the bulk material surface. The bulk material size was proportional to the bulk material strength, and the bulk material diameter was larger. Parts are smaller than 50mm, so 26GHz is currently the best choice for bulk sizing.
For some small tank applications with smaller diameter and lower height, the length of the 6GHz radar antenna (300-400mm) invisibly increases the blind area (about 600mm), which overcomes the multipath reflection caused by the poor directivity (larger angle) of the 6GHz radar. ; 26GHz radar has high frequency, short antenna and good directivity, which overcomes the shortcomings of 6GHz radar and is suitable for small tank measurement.
Due to the harsh on-site environment, over time, the radar antenna will accumulate dirt, water vapor, etc. The 26GHz antenna is small in size, and the addition of a radome can greatly improve the impact of water vapor; the 6GHz radar antenna is bulky, and it is difficult to add a radome. Moreover, the instrument is heavy and difficult to clean.
Because of the good directionality of 26GHz radar, many harsh working conditions can be measured by simply isolating the radar in a container.
The limitations of radar level gauges include the following:
The influence on the performance of the radar is the dielectric constant. In theory, the attenuation of the radar in the vacuum environment is very small. When there are radar attenuators in the air, such as high dielectric powder (graphite, iron alloy, etc.), water vapor If the volume is large, the measurement distance and effect will be affected.
Volatile gases in the measurement medium will gather on the antenna, and water vapor will gather on the antenna. At this time, the emission of radar waves will be affected, and radar waves will not be able to be emitted in severe cases.
The dielectric constant of the measuring medium should not be too small.
Although the temperature and pressure have little effect on the radar, the limitations of the radar antenna receiving materials and the use range of the radar to adapt to the temperature and pressure are related to the materials used and the sealing structure.
At present, radar level gauges have become the mainstream products on the market, and although low-frequency radar level gauges have a lower price advantage, they are all outdated products in the main application fields. Through the application of the ultrasonic level meter, in order to obtain a better echo signal, the operating frequency of the sensor is about 40KHz, the wavelength is about 9mm, and the opening angle of the transmitted wave is 7°-8°. The higher the operating frequency, the smaller the opening angle, but the smaller the measurement range; with ultrasonic simulation, the echo obtained by the radar level gauge has the above effect, the operating frequency should be 26GHz, and the wavelength at this time is 11mm. When using 100mm caliber, the emission wave with an opening angle of 7°-8° can be obtained. If the operating frequency of the radar is 6GHz, then the same operating frequency as the ultrasound is 10KHz. However, when the ultrasonic level meter with a working frequency of 10kHz measures the solid material level, its various indicators are not ideal, especially it is not suitable for measuring the solid material level.