Basic Knowledge Of Radar Level Meter
Author:Vacorda Source:www.vacorda.com Date: 2020-09-09 17:36:00
In the instrument circle, there are many kinds of level meter, and the products are 5 flowers and 8 products. In the previous content, we are familiar with the level switch, radio frequency admittance level gauge, magnetic flap level gauge, etc...
As one of the common level gauges, radar level gauges or non-contact measuring instruments are a very practical choice.
So, let's uncover the mystery of the radar level gauge for everyone at this moment!
Radar level meter is a common product type of level meter.
● It has the advantages of accurate measurement, robust efficiency, high reliability, and wide range of practical applications.
● It can be installed in various metal and non-metal containers or pipelines to stop measuring the level of liquid, slurry and granular materials.
● It is suitable for occasions where dust, temperature and pressure are changed greatly, and inert gas and steam exist.
Level ｜ Questions and Answers
How to classify radar level gauges?
What are the actual uses?
Radar level gauges can be divided into two categories according to the working door.
Non-contact (air-air radar) radar level gauge
Non-contact radar level gauges often use horns or rod antennas to emit and receive microwaves, and are not in conflict with the measured medium. They are installed on the top of the silo, and the microwaves propagate and go in the upper space of the silo.
Non-contact radar level meters can be divided into pulse radar level meters and frequency modulated continuous wave radar level meters according to microwave waveforms.
Contact radar level gauge
Contact radar level gauges use metal waveguides (rods or steel cables) to conduct microwaves. The instrument is installed from the top of the silo, and the guided waves reach the bottom of the silo. The emitted microwaves propagate down the inside of the waveguide before reaching the material. When the surface is reflected, it is received along the waveguide to the transmitter.
This type of radar level meter, which is directly used to measure the material measured by the guided wave line or probe, is mainly guided wave radar level meter, which can be further subdivided according to the difference of the metal waveguides adopted. It is: cable type (single/double), rod type (single/double) and coaxial guided wave radar level gauge.
Compared with contact radar level gauges, non-contact radar level gauges have the advantages of cumbersome installation, less cherished amount, sensitive use of door diameters, and freedom from the influence of factors such as dust and temperature in the warehouse. It is the one that has stagnated the fastest in recent years. Kind of measuring instrument.
Pulse radar level gauge
The pulse radar level gauge will emit microwave pulses that travel at the speed of light (in the atmosphere) and hit the surface of the measured medium (the dielectric constant must be greater than the dielectric constant of the propagation medium), and all the microwaves are reflected back (the amount of reflection depends on the material Surface flatness/dielectric constant size), accepted by the same antenna.
The greater the reflection (rate) of the medium, the stronger the signal, and the better the measurement; the smaller the reflection (rate), the weaker the signal, and the more cumbersome it is to be disturbed by disturbances.
Accurately identify the cutoff Δt between the transmitted pulse and the time of receiving the pulse, so as to further calculate the cutoff D from the antenna to the surface of the measured medium.
Frequency Modulation Continuous Wave Radar Level Meter (FMCW)
FMCW radar uses 24 GHZ as the measurement base frequency (carrier frequency), 2 GHZ is to adjust the bandwidth, all the scanning time is 7 ms, and a linear scan is realized. After the signal is transmitted, after the definite time delay of the process, it will bear the return. Wave signal.
In the linear frequency sweep, the vitality of the time difference occurs, which separates the proportional liquid level. Because there are many reflections, the fast Fourier transform (FFT) of all the echo time is stopped, and the time of the time signal is converted into a certain energy. The signals with high and steep video spectrum are useful signals.
Guided wave radar level gauge
Guided wave radar sends high-frequency microwave pulses along the detection component (steel rope or steel pipe).
When it hits the measured medium, due to the gradual change in dielectric constant, it causes emission, and all pulse energy is emitted back. The isolation and separation of the transmitted pulse and the reflected return pulse is proportional to the separation of the measured medium.
Radar level gauges are used in a wide range of scales, covering power, steel, metallurgy, cement, kerosene, papermaking, food and other scales. However, radar level gauges that use different principles have different management and utilization conditions.
The pulse radar level gauge is the same as the daily flat or used for all kinds of useful purposes, mainly for the liquid level measurement of the cylindrical, 35-meter tank medium.
However, for spherical tanks with mixing efficiency of liquid storage tanks, it is necessary to use guided wave radar level meters to stop measurement.
For containers or storage tanks with a large range and large dust, it is necessary to use a frequency-modulated continuous wave radar level gauge with high energy and strong resistance to disturbances.