Radar Lecture | Differences between Radar Level Gauges and Guided Wave Radar Level Gauges

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Radar level gauges are now used as standard instruments in various industries. However, many people often cannot distinguish between radar level gauges and guided-wave radar level gauges. This article will provide you with a detailed introduction. 1. Different working principles: The basic working principle of a radar level gauge is transmission–reflection–reception. The antenna of the radar sensor emits electromagnetic wave signals in the form of beams; the emitted waves are reflected by the surface of the material being measured, and the reflected echo signals are once again received by the antenna. Each point in the transmitted and reflected beams is acquired using ultrasonic sampling. After being processed by the intelligent processor, the signal determines the distance between the medium and the probe, which is then sent to the terminal display for display, alarm generation, operation, and more. The guided wave radar level gauge is a measuring instrument based on the time-of-travel principle; radar waves travel at the speed of light, and the travel time can be converted into a level signal using electronic components. The probe emits high-frequency pulses that travel along the cable-like probe; when these pulses encounter the surface of the material, they are reflected back and captured by a receiver within the instrument, which then converts the distance signal into a level signal. 2. Different contact methods: Radar level gauges are non-contact, while guided wave radar level gauges are contact-type. In other words, waveguide types cannot be used in applications with high requirements for food grade. 3. Different operating medium conditions: Guided wave radar level gauges must take into account the corrosiveness and viscosity of the medium, and longer guided wave radar systems are more difficult to install and maintain. In conditions of low dielectric constant, both radar and guided-wave radar rely on the difference in the dielectric constant of the medium for their measurement principles. Since the waves emitted by conventional radar are divergent, when the dielectric constant of the medium is too low, the signal becomes too weak, resulting in unstable measurements. In contrast, the waves from guided-wave radar propagate along the guided wave rod, making the signal relatively stable. Additionally, most guided-wave radars have a bottom detection function that allows for corrections based on the signals reflected from the bottom, thereby enhancing the stability and accuracy of the signals. 4. For selection purposes, ordinary radars can be used interchangeably, whereas guided wave radars cannot be interchanged since the length of the guided wave rod (cable) is fixed based on the original operating conditions. As a result, selecting a guided wave radar is more complicated than selecting an ordinary radar. 5. Different measurement ranges: Conventional radars are commonly used for tanks with a range of 20 or 30 meters. Guided wave radar also needs to take into account the stress on the guided wave rod (cable); it is due to this stress that the measurement range of guided wave radar is generally not very long. Guided wave radar has clear advantages in certain special operating conditions, such as when there is stirring inside the tank or significant fluctuations in the medium; in such situations, the measurement values obtained using a guided wave radar fixed at the bottom are more stable than those from ordinary radars ； There is also level measurement in small tanks; due to the limited space available for installation (or the presence of many obstacles inside the tank), conventional radars are generally not suitable. 6. Different styles: Radar level gauges have a trumpet-shaped design, while guided wave radar level gauges feature a guided wave rod. Since the two shapes are different, they will naturally perform differently in some applications.