1. Measuring principle of radar level meter
The radar liquid level meter adopts the operating mode of transmitting -reflection-receiving.The antenna of the radar level meter emits electromagnetic waves,which are reflected by the surface of the measured object and then received by the antenna.The time from transmitting to receiving of electromagnetic waves is proportional to the distance to the liquid surface.The formula is as follows: D=CT/2
In the formula, D——the distance from the radar level meter to the liquid level; C——the speed of light; T—— the running time of electromagnetic waves.
Radar level meter records the duration time of pulse wave,and the transmission speed of electromagnetic wave is constant, then the distance from the liquid surface to the radar antenna can be calculated to know the liquid level of the liquid surface.
In practice, there are two ways for radar level meters,namely, frequency-modulated continuous wave and pulse wave.The liquid level meter adopting the frequency-modulated continuous wave technology has large power consumption and must adopt a four-wire system, and the electronic circuit is complicated.The liquid level meter using radar pulse wave technology has low power consumption and can be powered by two-wire system 24V DC, which is easy to achieve intrinsic safety, high accuracy and wider application range.The VEGAPULS radar level meter uses pulsed microwave technology.Its antenna system emits a pulse beam with a frequency of 6.3 GHz and a duration time of 0.8 ns,and then pauses for 278 ns.During the pause period of the pulse transmission,the antenna system will act as a receiver,receive the reflected wave, and simultaneously perform echo image data processing to give the indication and the electric signal.
2. Characteristics of radar level meter
(1) Radar level meter adopts integrated design ,without movable parts,no mechanical wear, long service life.
(2) The electromagnetic wave emitted by the radar level meter can pass through the vacuum without any transmission medium, and has the characteristics of being free from the influence of the atmosphere, steam and volatile fog in the tank, and can be used for the liquid level measurement of the volatile medium,such as crude benzene.
(3) The radar level meter can be used for liquid level measurement of almost all liquids.When the electromagnetic wave is reflected on the surface of the liquid level, the signal will attenuate.When the signal attenuates too much,the radar level meter can not detect enough electromagnetic wave signal. Conducting medium can reflect electromagnetic wave well.For the VEGAPULS radar level meter, even micro-conducting substances can reflect enough electromagnetic waves.Non-conductive media with dielectric constant greater than 1.5 (the dielectric constant of air is 1.0) can also ensure sufficient reflected waves,and the larger the dielectric constant, the stronger the reflected signal. In practical,almost all media can reflect enough reflected waves.
(4) Non-contact measurement is adopted, which is not affected by physical properties such as density and concentration of liquid in the tank.
(5) The measuring range is large, and the largest measuring range is 0~35m,which can be used for liquid level measurement of high temperature and high pressure.
(6) The antenna and other key components are made of high-quality materials, which have strong corrosion resistance and can adapt to a strong corrosive environment.
(7) Rich in functions,with a false wave learning function. Enter the actual liquid level of the liquid level,the software can automatically identify the false echo from the liquid level to the antenna,and eliminate the interference of these waves.
(8) The parameter setting is convenient,and can be set by the simple operation key on the liquid level meter.It can also be set remotely or directly to the communication end of the level meter by using the HART protocol operator or a PC equipped with VEGA Visual Operating software.