Brief introduction of radar level gauge

1. Basic principle Radar wave is a special form of electromagnetic wave. Radar level gauge uses the special performance of electromagnetic wave to detect material level. The physical characteristics of electromagnetic waves are similar to those of visible light, and their propagation speed is equivalent to the speed of light. Its frequency is 300MHz-3000GHz. Electromagnetic waves can penetrate interference sources such as space steam and dust, and are easily reflected when encountering obstacles. The better the conductivity of the measured medium or the greater the dielectric constant, the better the reflection effect of the echo signal. The higher the frequency of the radar wave, the smaller the emission angle, the greater the energy (magnetic flux or field strength) per unit area, the smaller the attenuation of the wave, and the better the measurement effect of the radar level gauge. Transmit-reflect-receive is the basic working principle of radar level gauge. The antenna of the radar sensor emits a minimum 5.8 GHz radar signal in the form of a beam. The reflected signal is still received by the antenna, and the running time of the radar pulse signal from transmission to reception is proportional to the distance from the sensor to the surface of the medium and the level of the material. That is: h= H–vt/2 where h is the material level; H is the tank height; v is the radar wave velocity; t is the interval time from radar wave transmission to reception 2. The advanced technology of radar level gauge to measure material level: (1) The application of new echo processing technology. The radar level gauge can be known from the measurement principle of the radar level gauge. The radar level gauge measures the material level by processing the time when the radar wave is emitted from the probe to the surface of the medium and then returns to the probe. Yes, there are many interference signals mixed in the reflected signal, so the processing of the real echo and the identification technology of various false echoes become the key factors for the accurate measurement of the radar level gauge. (2) Measurement data processing: Due to the influence of factors such as liquid level fluctuations and random noise, there must be a lot of noise mixed in the detection signal. In order to improve the accuracy of detection, the detection signal must be processed to eliminate noise as much as possible. After a lot of experimental verification, the data smoothing method can achieve satisfactory results. This method can also effectively overcome the influence of the agitator in the tank on the measurement. (3) Features of the radar level gauge: Since the radar level gauge adopts the above-mentioned advanced echo processing and data processing technology, coupled with the characteristics of high frequency and good penetration performance of the radar wave itself, the radar level gauge has the characteristics of Better performance than contact level gauges and similar non-contact level gauges. ①It can be measured continuously and accurately under harsh conditions. ②Simple operation and convenient debugging. ③ Accurate, safe and energy saving. ④ No maintenance and high reliability. ⑤ Almost all media can be measured. 3. Problems that should be paid attention to in installation (1) When measuring liquid materials, the axis of the sensor should be kept perpendicular to the surface of the medium; when measuring solid materials, the sensor should be inclined at a certain angle because the solid medium has a pile angle. (2) Try to avoid devices that cause false reflections within the emission angle. In particular, it is necessary to avoid obstacles in the 1/3 cone-shaped emission area closest to the antenna (because the closer the obstacle is, the stronger the false reflection signal is). If it is unavoidable, it is recommended to use a refraction plate to refract the excessively strong false reflection signal. This can reduce the energy density of false echoes, making it easier for the sensor to filter out false signals. (3) Avoid the feed port to avoid false reflections. (4) The sensor should not be installed in the center of the arched tank (otherwise the false echo received by the sensor will be enhanced), and it should not be installed very close to the tank wall. The best installation position is 1/2 of the radius of the tank. (5) Avoid installing in places with strong eddy currents. For example: due to stirring or strong chemical reaction, etc., it is recommended to use waveguide or bypass tube for measurement. (6) If the sensor is installed on the tube, the antenna must protrude from the tube. The horn antenna protrudes at least 10mm from the tube. Rod antennas take over lengths up to 100 or 250mm. Take over the minimum diameter of 250mm. The method of increasing the diameter of the connecting pipe can be adopted to reduce the interference echo generated by the connecting pipe. (7) Regarding the waveguide antenna: the inner wall of the waveguide must be smooth, and the bottom opening of the waveguide must reach the required minimum liquid level, so that it can be measured in the pipeline. The type plate of the sensor should be aligned with the axis of the waveguide opening. If the measured dielectric constant is less than 4, it is necessary to install a reflector at the end of the waveguide, or bend the end of the waveguide into a curvature to refract the reflected echo at the bottom of the container. 4. Problems and solutions in the application, the radar level gauge used in some working conditions, due to the improper installation position and conditions of the sensor, some problems have appeared, the following will propose solutions to some problems in use, for For your reference. the

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