What is radar level transmitter frequency range? When purchasing radar level gauges, users often encounter different specifications and models. The most common are different measurement frequencies. Such as 8GMHz, 26GMHz, 80GMHz, 120GMHz, etc. All are radar gauges, why are the frequencies so different? What are the advantages and disadvantages of different frequency products? I hope that through the introduction of this article, you can choose a radar level gauge product suitable for measuring working conditions when purchasing a radar level gauge.

Radar Level Transmitter Frequency Range

classification of radar level transmitter frequency range

The radar level Transmitter is a measuring instrument based on electromagnetic wave emission and reflection reception to judge the level of material. According to the type of transmitted signal, it is divided into two categories: pulse radar and frequency modulation continuous wave radar.

Pulse radar is measured based on time domain reflectometry (TDR). That is, the radar antenna emits high-frequency pulse electromagnetic waves, which propagate at the speed of light.

When encountering the surface of the measured medium, part of the pulse of the radar level Transmitter is reflected to form an echo back To the pulse emission device. The distance between the emission device and the surface of the measured medium is proportional to the propagation time of the pulse. The height of the liquid level is obtained by calculation.

Frequency modulation continuous wave radar is based on the frequency difference of frequency modulation continuous wave (FMCW). That is, the radar uses synchronous frequency modulation technology. The transmitter and receiver are installed on the top.

The transmitter emits a microwave signal whose frequency has been linearly modulated to the liquid surface. When the microwave When the signal propagates down to the liquid surface and is reflected back to the receiver. Due to the time delay, the frequency of the transmitted signal changes. The distance passed by the radar wave is calculated by the frequency difference between the received reflected wave and the transmitted wave.

Generally speaking, the larger the frequency modulation range, the longer the measurement distance, the better the linearity and the higher the resolution.

Microwave refers to electromagnetic waves with frequencies ranging from 300MHz to 3x103GHz, and their corresponding wavelengths range from 0.1mm to 1m. This segment of the electromagnetic spectrum includes decimeter waves (frequency range 300MHz~3GHz), centimeter waves (frequency range 3~30GHz), millimeter waves (frequency range 30~300GHz) and submillimeter waves (frequency range (300MHz~3x103GHz) ) four bands.

The common radars on the market are 6GHz, 26GHz and 80GHz that appeared in the last two years. The wavelength of the 6GHz radar is 50mm, and the wavelength of the 26GHz radar is 11mm, both of which are centimeter wave radars. They belong to microwave radars that work in the centimeter wave band for detection. The wavelength of the 80GHz radar is 4mm, which belongs to the millimeter wave radar working in the millimeter wave band.

Comparison of different frequency radar level transmitters

The frequency of the guided wave radar level meter is generally 6.3GMHz and 8GMHz, which are centimeter wave radar waves.

In terms of operating principle, guided wave radar is very similar to conventional radar that propagates electromagnetic waves through space.

The basis of guided wave radar Level Transmitter is the principle of time domain reflection of electromagnetic waves.

Through this principle, buried cables and high cable breaks buried in walls can be found.

When measuring a broken end of a cable, the electromagnetic pulse signal sent by the TDR generator propagates along the cable, and when it encounters a broken end, a measurement reflected pulse will be generated.

At the same time, fundamental pulses are also caused by changes in the impedance of the total length of the preset cable in the receiver.

Compared with the basic pulse, the reflected pulse can accurately measure the position of the broken end.

Guided wave radar Level Transmitter Advantages:

  1. The ability to suppress steam and foam is strong, and the measurement will not be affected.
  2. High performance, high precision, high reliability, low maintenance and long service life.
  3. The porosity of solid materials is not affected by liquid density, temperature and dust.

Guided wave radar Level Transmitter Disadvantages:
Guided wave radar Level Transmitter is a contact radar, and generally cannot be used in places with high hygiene requirements such as food, biology, and pharmaceuticals.

The frequency of the pulse radar Level Transmitter is generally 26GGMHz, which is a centimeter wave radar wave.

High-frequency pulse radar is used to modulate microwave source signals with narrow pulses. After reflection on the surface of the medium, pulse waves of fixed frequency (ie, carrier frequency) are emitted in the form of beams.

The time course of the pulse determines the distance from the transmitting antenna to the surface of the medium.

For ordinary pulse radar, the accuracy can generally reach ±3~±10mm;

For ordinary pulse radar, the range can generally reach 30M;

For ordinary pulse radar, physical properties such as volatilization and crystallization of the measurement medium may affect;

Advantages of Pulse Radar Level Transmitter:

  1. Integrated structure, non-contact horn.
  2. The measurement range is large and the measurement error is small.
  3. Advanced multi-functional software can eliminate the interference of agitators or other obstacles, and is not affected by temperature, dust, and steam.
  4. Wide range of applications, mostly used in oil storage tanks, asphalt storage tanks, petroleum liquefied gas, reactors, measuring the continuous liquid level of sewage tanks in petrochemical industry and blast furnace steel in steel industry, and measuring in the brewing process. Food industry, pharmaceuticals Liquid level measurement is also widely used in other fields.

Disadvantages of Pulse Radar Level Transmitter:

  1. Most economical pulse microwave level gauges use 55.8GHz or 6.3GHz with a large radiation angle (about 30°), and the container wall or internal components are prone to interference echoes.
    Although increasing the size of the horn antenna can slightly reduce the emission angle. However, due to the increased volume, it is inconvenient to use.
  2. When there is an agitator in the tank, when obstacles such as pipelines appear, these obstacles will also reflect electromagnetic wave signals, thus generating false liquid level signals.
  3. When the liquid level fluctuates and bubbles, the situation becomes more complicated. The signal scattering is separated from the transmission or absorbs most of the energy. This results in a weak or no signal returning to the radar Level Transmitter receiving antenna.

The frequency of continuous wave radar Level Transmitter is generally 80GMHz, 120GMHz, millimeter wave radar wave.

Frequency modulation continuous wave radar, the signal is sent from the antenna, and the echo is received by the antenna after being reflected by the measured medium.

The transmitted signal frequency is proportional to the difference in frequency received by the echo.

After FFT, the frequency difference is converted into a spectral difference, and then converted into a measurement distance.

The total range minus the measurement distance is the actual liquid level.

For FM CW radar, the accuracy can reach ±1mm.

For FM continuous wave radar, the maximum range can reach more than 1000M.

For frequency-modulated continuous wave radar, its beam angle is small, its energy is concentrated, and its permeability is strong. It is suitable for harsh conditions such as violent liquid level fluctuations and stirring.

Advantages of FM Radar Level Transmitter:

Due to the characteristics of the FM continuous radar itself, compared with the pulse radar, it has the advantages of small blind spots and low interference probability.

In addition, the radar of the system can perform speed measurement, distance measurement, angle measurement and other operations at the same time, and can obtain rich target positioning information.

It is worth noting that the frequency of the difference frequency output signal of the radar is low, which reduces the difficulty of hardware design for signal processing.

Frequency modulated continuous wave radar can be widely used in scenarios such as vehicle collision avoidance, liquid level measurement, assisted parking, and vital sign detection.

The successful development of radar is for the national economy. It plays a great role in promoting the development of national defense.

At present, the 1200 millimeter-wave radar Ghz frequency band is mainly used, which greatly reduces the antenna size and continuously improves the product integration.

Using 120GHz combined with a lens antenna, the beam angle of the radar can be narrowed to 4°. The internal measurement is close to the lidar, and the anti-interference performance is much better than that of the lidar.

Disadvantages of FM Radar Level Transmitter:

The manufacturing cost of radar Level Transmitter is relatively high.

The pulse/FM radar antenna is made of stainless steel and PTFE, and the maximum operating temperature of PTFE is 200° and the maximum pressure is 4MP. When the guided wave radar is composed of stainless steel and ceramics, the maximum operating temperature is 400° and the maximum pressure is 40MP.

The low-frequency radar level transmitter is still the first choice for the low-frequency radar level transmitter and cannot be completely replaced.

Effect of radar level transmitter frequency range on measurement

The radar level gauge emits electromagnetic waves through the antenna. The higher the frequency of the electromagnetic wave, the higher the energy of the electromagnetic wave. The shorter the wavelength, the more obvious the scattering phenomenon. Conversely, the lower the energy, the longer the wavelength, and the energy is not easily absorbed by the gas phase layer.

For the same size antenna, a liquid level sensor with a wavelength of 1.2 cm and a frequency of 26 GHZ has a gain of 6 times higher than that of a liquid level sensor with a wavelength of 3 cm and a frequency of 10 GHZ. (Remarks: Antenna gain is a parameter indicating the degree of radiation concentration of a directional antenna).

The overall beamwidth of a radar level gauge is inversely proportional to the frequency of the device. Therefore, for the same diameter antenna, if the frequency of the radar level gauge is increased, the beam width will be lower than that of the lower frequency equipment, and the narrow beam can minimize the influence of the nozzle, tank wall and interference.

At the same time, the measurement range of the radar level gauge is also affected by factors such as frequency, antenna size, dielectric constant of the liquid, and process conditions.

Featured Radar Level Transmitters

The difference in application of radar level transmitter frequency range

Dirty and polluted environment

With long-term use, dirt and pollutants accumulated on the antenna will affect the strength and direction of the radar signal. For high frequency signals, any dirt that covers the antenna will absorb more energy, and the direction of the beam may change. This results in a loss of signal strength. So, low-frequency and medium-frequency technologies are more suitable.

Storage tanks with condensate and/or steam

Condensation and steam can cause reflections on product surfaces to be masked by the “noise” of water droplets. This is more of a problem for high frequency signals. So mid and low frequency techniques are a better choice. Antennas with flat, horizontal surfaces should always be avoided for condensation.

High steam and agitation

Be sure to choose the 80G millimeter-wave radar level meter. The 80G radar level meter has a high transmission frequency and has good penetration and is not affected by steam. The 2° transmission angle can effectively avoid the interference of the stirring blade. The unique echo Tracking algorithm avoids reading multiple echoes when the material level is high.

Applications with turbulence, waves and ripples

Waves and ripples are often found on the surface of process liquids in large tanks. And this turbulence is especially detrimental to high-frequency measurements. Low and mid frequency level instruments emit longer wavelengths, making them perform better.

Foam application

Like dust and condensation, a layer of foam on top of the liquid can absorb the radar signal, making accurate measurements more difficult. Low frequencies work best with thick foams, such as beer, molasses, or latex. For lighter foam, the mids perform well. High frequency techniques should be avoided in foam applications.

Read more about: Stilling Wells for Radar Level Measurement

Bulk liquid storage tank

Many bulk storage tanks use floating roof tanks that require level measurement through stilling pipes. Low frequency radars are preferred for these applications as they are less sensitive to buildup on pipe walls. Except in not perfectly straight tanks and pipes. High frequency radars would have difficulty in this situation.

Small and medium container

These vessels are often up to 20 meters (m) high and often present challenging conditions. such as condensation, contamination, turbulence and foam. IF technology is a good choice in this tank because it combines small antennas with good reliability.

Small tank/bucket

In small tanks approximately 0.5 to 1.5 m high, the size and position of the nozzles may be restricted. Short measurement ranges and the need for small antennas mean that HF and MF technologies are attractive options for these applications.

Solid level

For measuring the level of solids, the optimum frequency depends on the application. Low and mid frequencies can handle dust, condensation and coarse solids. High frequency is suitable for fine powder.

Condensation is often challenging for high-frequency radars. But with solids another problem arises: Condensation combined with certain types of solids can lead to rapid buildup of material. This quickly clogs the small nozzle opening and covers the small antenna of the high frequency radar.

Read more: The Impact of Frequency in Non-Contacting Radar Level Measurement by Emerson

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About What Is Radar Level Transmitter Frequency Range? I hope that through this article, you can have a detailed understanding. Frequency band selection is an important consideration when deciding which non-contact radar device is the best choice for each different level measurement application.

The difference in the application of radar level transmitter frequency range is summed up after our many years of experience.

When measuring steam and foam, and condensate, choose low-frequency radar first.
In most other applications, high frequency radars are preferred for ease of installation. Lower frequencies reduce sensitivity to vapor, foam and antenna contamination.
Low frequency radars have a wider beam velocity angle to better deal with steam, dust, condensation, contamination and turbulent surfaces.
Higher frequencies minimize the effect on nozzles, tank walls and disturbances.

If you need to choose radar level transmitter, or still have doubt about radar level transmitter frequency range. Please feel free to contact our sales engineers.

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