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Focus On Level Measurement
How To Achieve The Best Performance Of Radar Level Meter?
The beam Angle configured for the radar transmitter does not cross with the vessel wall or obstacles, which is the ideal situation.
However, it is important to understand that even if the beam intersects with an obstacle or wall, this does not necessarily mean that the installation will not succeed.Intersecting with a wall may cause some loss of energy, but it is often insignificant.
Obstacles in the beam path can be mapped to eliminate their effects from the signal evaluation.
It is often considered that if the beam Angle intersects the vessel wall, it is not suitable for the application of free-space radar.When the radar is installed, it is ideal that the beam Angle does not intersect with the vessel wall.The successful implementation of most applications can be ensured by selecting the appropriate frequency, antenna size, and container mapping.
Frequency and antenna size affect the measurement range.However, the dielectric constant of the measured material and the installation condition of the measurement have great influence on the measuring range.
Low-frequency signals have longer wavelengths and can travel longer distances than high-frequency signals.The high-frequency radar transmitter has a measuring range of about 100 feet, which is enough for most applications.
The size and type of antenna also affect the transmission distance.Large antennas transmit farther distances than small ones, and they focus more energy.Horn antenna, "teardrop" antenna, "parabola" antenna, rod antenna, and flat antenna are all antenna styles used to meet different application requirements and measurement range.
Installation conditions for radar transmitters
Even with the best radar, there are consequences if it is not installed properly.Existing conditions must be considered in the installation.The permittivity of the material under test, the type of installation, the location, and the target surface all have an effect.
Condensation, usually caused by water on the antenna of a radar transmitter, can cause problems.The dielectric constant of water is up to 80dc.In a typical horn antenna, water droplets condense inside the horn, causing interference and affecting the emission of electromagnetic signals.This interference causes "noise" in the signal and reduces energy.If there is enough condensation, it can cause the radar to lock into the proximity zone, causing a malfunction.
To solve the problem of condensation, several special antenna designs have been developed to avoid the effects of "condensation".If the traditional horn antenna must be used under application conditions, a purge line can be added to prevent radar condensation or dust accumulation.Because of its low dielectric strength, air does not interfere with microwave signals.A common and effective way to keep the horn clean is to purge it with air at a pressure of 60 to 70 psi, such as the shock wave activated by the solenoid valve.
Some manufacturers provide diagnostic capabilities to monitor the coupling zone.When condensation or ash reaches a certain level, it can interfere with signals.These advanced diagnostic features can be used for maintenance, such as purging antennas before they fail.Provide preventive maintenance capability to reduce downtime and emergency capacity maintenance requirements.
Obstacles inside the container must be considered.Agitators, heating coils, sleeves, and other components inside containers can interfere with radar transmissions.The 80 GHz radar has a narrow beam Angle, which is effective in avoiding most obstacles.The remaining unavoidable parts need to be eliminated from the signal evaluation to prevent the transmitter from treating obstacles as false level signals.
Figure 2: the envelope curve of agitator signal is shown in the figure.
Normally, jamming signals are "eliminated," so radar transmitters ignore them.Figure 2 shows the level measurement signal evaluation without agitator interference.The red line in figure 2 is the signal provided by the returned microwave energy.The black line eliminates the signal reflected by the agitator, so that the transmitter only calculates the actual level signal.For signals that are valid and considered material level, the signal level must be higher than shown in the figure.
Not only the frequency of the radar, antenna design, intelligent algorithm and installation location also play an important role in the successful measurement of the material level of the tank or silo.The more complex and precise the application, the more critical it is to obtain the optimal frequency and antenna design.