80 GHz Radar Level Measurement
80GHZ Radar Level Transmitter refers to a frequency modulated continuous wave (FMCW) radar product operating at 76-81GHz. It can be used for level measurement of solids and liquids. Since it operates at a higher frequency, the wavelength is shorter. It has a smaller diameter. Ideal for dusty atmospheres or low reflective media. It has unique advantages in high dust and harsh temperature environment (+200℃). Small dead zone and narrow beam angle allow use in small and tall vessels.
Unique Technical Advantages of 80GHZ Radar Level Transmitter
80GHZ Radar Level Transmitter refers to frequency modulated continuous wave (FMCW) radar products operating at 76-81GHz. Four-wire and two-wire applications are supported. There are multiple models, the maximum range of the product can reach 120m, and the blind area can reach 8 cm.
Because the 80GHZ Radar Level Transmitter operates at a higher frequency. shorter wavelengths. So it is especially suitable for solid applications. The working method of transmitting and receiving electromagnetic waves through a lens. It has unique advantages in high dust and harsh temperature environment (+200℃).
80GHZ Radar Level Transmitter provides flange or threaded fixing, which makes installation convenient and easy.
The main advantages of 80GHZ Radar Level Transmitter are as follows:
- Based on self-developed CMOS millimeter-wave radio frequency chip. Enables a more compact RF architecture. Higher signal-to-noise ratio, smaller dead zone.
- The 5GHz operating bandwidth enables the product to have higher measurement resolution and measurement accuracy.
- The narrowest 3° antenna beam angle. Disturbances in the installation environment have less impact on the meter. Installation is more convenient.
- Shorter wavelengths and better reflection properties on solid surfaces. Therefore, there is no need for special use of universal flanges for aiming.
- Support remote debugging and remote upgrade. Reduce waiting time. Improve work efficiency.
- Support mobile phone Bluetooth debugging. It is convenient for on-site personnel to maintain work.
Extended reading: Non contact level measurement
Communication and debugging
The instrument can be debugged through the LCD in the field. It can also be debugged on the PC side with the optional host computer software.
The communication between the 80GHZ Radar Level Transmitter and the PC is as follows:
- USB to RS485 serial cable (four-wire system);
- USB to TTL serial cable (two-wire system);
- USB to Hart-modem (two-wire system) for communication.
- Debugging through bluetooth through mobile phone makes on-site debugging safer and more convenient.
- 4G network, remote debugging through remote module.
Extended reading: Radar Level Sensor Advantages and Disadvantages
80GHZ Radar Level Transmitter Measurement Principle
The general principle of the FM continuous wave radar level gauge is that the radar emits electromagnetic waves on the top of the tank. And the electromagnetic waves are received by the radar after being reflected by the medium.
The frequency difference δf between the received signal and the transmitted signal is proportional to the distance R from the surface of the medium:
R=C (speed)*δf (frequency difference)/2/K (frequency modulation slope).
Because the speed of light C and the frequency modulation slope K are known.
The frequency difference δf can be estimated to obtain the distance R from the radar installation position to the material surface.
And then through the known total height of the tank. Subtract the spatial distance from the radar to the material surface (referred to as Empty height) to get the height of the material level.
Extended reading: Magnetostrictive Level Transmitter Working Principle
Terminology
Beam angle:
Beamwidth bounded by 3dB below the maximum value. The minimum beam angle of 80GHZ Radar Level Transmitter is 3°, as shown in the figure.
Distance Resolution:
Range resolution refers to the radar’s ability to distinguish between two objects that are very close together.
If the separation between the two objects is less than the range resolution of the level radar. Then the radar can only measure one distance value. This distance value is not equal to the distance value of any of the objects. It is a combination of the distance values of the two objects.
The FM bandwidth of the 80GHZ Radar Level Transmitter is B=5.1GHz. Minimum distance resolution=C/2B≈3cm.
Measurement accuracy (Accuracy):
If there is only one object and this object has moved a small distance. Whether the level radar can detect distance changes. The indicator of how far a single object has moved is called accuracy.
The IF signal of the 80GHZ Radar Level Transmitter is analyzed by its own algorithm, and the measurement accuracy is 0.1mm.
Ambient temperature:
The temperature of the surrounding air in contact with the device enclosure.
Blind spot:
Refers to the measurement limit of the near end of the instrument, and the instrument cannot measure in the blind area.
dB (decibel):
Indicates the unit of signal amplitude.
Dielectric Constant (DK):
The ability of a dielectric to store electrical energy under the induction of an electromagnetic field. Often referred to as the relative permittivity.
The increase in the permittivity is directly proportional to the increase in the echo amplitude. The relative vacuum/dry air dielectric constant is 1.
Echo:
The reflected signal received by the radar.
Emission cone:
The extension of the antenna beam angle.
False echo:
Any echoes that are not generated by the desired target. Generally, false echoes are generated by obstructions in the container.
Multiple echoes:
The multiple reflection echoes appearing at the target echo distance may be 2 or 3 times.
Polarization:
Emitted electromagnetic wave properties, describing the direction and magnitude of the electric field vector that changes over time.
Range:
(1) Refers to the farthest measurement limit of the instrument
(2) Special, refers to the artificially set maximum distance. Outside this distance, the meter does not consider it when processing data.
Repeatability:
In the same test environment, measure the same reflective target multiple times to measure the deviation of the results.
Speed of light:
Symbol C, the speed of electromagnetic waves. Includes electromagnetic waves and light in free space. The speed of light is 299,792,458 meters per second.
Threshold curve:
A time-varying curve that serves as a threshold beyond which echoes are considered valid.
Extended reading: Amazing Solutions for Continuous Liquid Level Measurement
Beam Angle
The beam angle is the beam angle when the radar wave energy density reaches half of its maximum value (3dB width). Microwaves emit signals outside the beam range and can be reflected by interference objects.
| Lens antenna diameter | Φ32mmLens antenna | Φ42mmLens antenna | Φ78mmLens antenna |
| Beam angle | 8° | 6° | 3° |
The larger the antenna size, the smaller the beam Angle alpha, the less the interference echo will be generated.
For more accurate measurements, avoid installing any internal devices (such as limit switches, temperature sensors, bases, vacuum rings, heating coils, baffles, etc.) within the signal beam range.
Linear
Extended Reading: What is level transmitter working principle?
80GHZ Radar Level Transmitter Applications
80G high frequency radar level meter has the characteristics of high measurement accuracy, wide application range, non-contact measurement, etc. It can be widely used in material level and liquid level measurement of various highly corrosive and high dust media.
The 80GHz radar level meter can not only measure the liquid level, but also measure the solid material level. Including powder materials. It has a good application in different storage tanks. Process storage tanks (silo), reaction tanks, static storage tanks , Dome tank, flat-top tank, spherical tank, horizontal tank, stilling pipe, bypass pipe, tank with agitator.
Applicable working conditions:
- Intermediate silo
- Warehouse
- hopper
- Storage tank
- Process tank
- Mixing tank
Extended reading: Oil-water interface measurement-Magtech magnetic level indicator
The micro-powder business department of a chemical plant has a variety of tanks, with a field measuring a range of 25 meters. There is a stirrer and heating device inside, and there is high steam when feeding.
As shown in the figure below, when the staff opened the observation cover, strong steam could be seen coming out.
A guided wave radar level gauge is selected before the scene. However, guided wave radar is easily affected by factors such as the corrosiveness of the measuring medium and the viscosity of the medium, and the measurement effect is not good.
Later, the customer chose the 80G radar level meter, and the historical trend chart after use is as follows. It can be seen that the liquid level of the four 80G radar level gauges installed on-site can be measured well in several loading and unloading processes.
Extended Reading: FMCW Radar for High Temperature Level Sensor
Why do we have to choose an 80G millimeter-wave radar level gauge for liquid level measurement under high steam and stirring conditions? Can the 26G radar level gauge measure?
Explain briefly. The 80G radar level gauge has a high transmission frequency, has good penetration, and is not affected by steam.
The launch angle of 3° can effectively avoid the interference of the stirring blade;
The unique echo tracking algorithm (echo locking function) avoids reading multiple echoes when the material level is high.
However, when the 26G radar level gauge is in a high-steam environment, the radar wave cannot penetrate the steam or the echo is greatly weakened after the radar wave reaches the interface of the medium, and the measurement is unstable;
In addition, the launch angle of the 26G radar level gauge is generally above 20°, so that the radar wave is easily affected by the stirring blade, causing false alarms;
And when the material level is high, there is no internal steam and the range is large, the echo is very strong, and it is easy to read multiple echoes.
Therefore, the 80G radar level gauge can be selected to obtain a good measurement effect for liquid level measurement under high steam and stirring conditions.
Extended reading: Radar Level Meter for Corrosive Liquids
So far, it is difficult for radar sensors to measure the level of very light medium and medium with low dielectric constant. Such as plastic foam, polystyrene, oil, etc. The difficulty of measurement is that the dielectric constant of these substances is very low and some media contain a lot of air. . So very little radar energy can be reflected.
Today we will share a related case: a petrochemical unit measures industrial white oil (dielectric constant <2). When the liquid level is low, as shown in the figure below, the liquid level is only about 50mm.
The user used a conventional 26G radar level gauge before. When there is only a small amount of white oil at the bottom of the tank, the radar wave directly penetrates to the bottom of the tank. Because the installation of the guided wave radar level gauge needs to reserve the bottom distance, it cannot be measured normally when the liquid level is relatively low.
Later, the customer chose the 76-81GHz FM continuous wave radar level gauge. The 80G radar level gauge has a 5GHz ultra-large FM scan frequency width. Compared with the ordinary 26G radar level gauge, the echo curve is shown in the figure below. The yellow curve can be seen The representative FM continuous wave radar level gauge. It can accurately read the material level height and tank bottom height. It can clearly distinguish the 50mm oil level height. The 26G radar level gauge represented by the gray curve cannot distinguish the correct liquid level. It penetrates directly through the interface and reaches the bottom of the tank.
The frequency modulation bandwidth of the 80G radar level meter is B=5.1GHz. The minimum distance resolution is Sres=C/(2×B)=2.94cm. Due to the wide frequency modulation bandwidth, the 80G radar level meter has a high resolution. Even if the bottom blind area is small, the meter can distinguish the correct liquid level.
Find more about Guided wave radar level transmitters equipped with Coaxial Probe for liquids with low dielectric constant. For example: non-ionized water, deoxygenated water and other liquid measurement.
Extended reading: Hydrostatic Level Measurement
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Wu Peng, born in 1980, is a highly respected and accomplished male engineer with extensive experience in the field of automation. With over 20 years of industry experience, Wu has made significant contributions to both academia and engineering projects.
Throughout his career, Wu Peng has participated in numerous national and international engineering projects. Some of his most notable projects include the development of an intelligent control system for oil refineries, the design of a cutting-edge distributed control system for petrochemical plants, and the optimization of control algorithms for natural gas pipelines.