What are the principles and characteristics of radar level gauges?

1. Measurement principle of radar level gauge


The radar level gauge uses a transmit-reflection-receive mode of operation. The antenna of the radar level gauge emits electromagnetic waves. These waves are reflected by the surface of the object to be measured and then received by the antenna. The time from the transmission to the reception of the electromagnetic wave is proportional to the distance from the liquid surface. The relationship is as follows:

D=CT/2

Where D is the distance from the radar level gauge to the liquid level

C——the speed of light

T——electromagnetic wave running time

The radar level gauge records the time elapsed by the pulse wave, and the electromagnetic wave transmission speed 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 gauges, namely, frequency-modulated continuous wave and pulse wave. The liquid level meter adopting the frequency modulation 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 24V DC, which is easy to achieve intrinsic safety, high precision and wide application range.

The VEGAPULS radar level gauge uses pulsed microwave technology. The antenna system emits a pulse beam with a frequency of 6.3 GHz and a duration of 0.8 ns, and then pauses for 278 ns. During the pulse emission pause, the antenna system acts as a receiver and receives reflected waves. At the same time, echo image data processing is performed to give an indication and an electrical signal.

 

2. Characteristics of radar level gauge

 

(1) The radar level gauge adopts integrated design, no moving parts, no mechanical wear and long service life.

(2) The electromagnetic wave emitted by the radar level gauge can pass through the vacuum, does not need the transmission medium, and has the characteristics of being free from the influence of the volatilization fog in the atmosphere, steam and tank, and can be used for the liquid level measurement of the volatile medium such as crude benzene. .

(3) The radar level gauge 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 be attenuated. When the signal decays too little, the radar level gauge cannot detect enough electromagnetic wave signal. The conductive medium can reflect electromagnetic waves well, and it can reflect enough electromagnetic waves to VEGAPULS radar level gauges and even micro-conducting materials. A non-conductive medium having a 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 applications, 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 key components such as the antenna are made of high-quality materials, which have strong corrosion resistance and can adapt to a highly corrosive environment.

(7) Feature-rich, 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 connected to the liquid level meter remotely or directly by the HART protocol handheld device or the PC equipped with VEGA Visual Operating software. It is very convenient to set the end.