Comparison between radar level gauges and guided wave level gauges

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In the chemical industry, level gauges are used on various tanks and containers. The two main types are radar level gauges and guided wave level gauges: Radar Level Gauge Principle: Transmission–reflection–reception is the basic working principle of a radar level gauge. 　　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, etc. 　　Feature: The biggest advantage of radar level gauges is their excellent performance under harsh conditions. It can measure both toxic and corrosive media, as well as solid, liquid, powdered, or slurry-form media. In terms of measurement, it has the following characteristics: 1. Continuous and accurate measurement. The probe of the radar level gauge does not come into contact with the surface of the medium; it is a non-contact measurement method that enables accurate and rapid measurement of different types of media. The probe is hardly affected by temperature, pressure, gases, etc. (the impact is only 0.018% at 500°C and 0.8% at 50 bar). 　　2. It has the capability to suppress interference echoes. 3. It is accurate, safe, and energy-efficient. Radar level gauges use materials with high chemical and mechanical stability, and these materials can be reused, making them highly environmentally friendly. 　　4. No maintenance required and high reliability 　Microwaves are hardly affected by interference, and since they do not come into direct contact with the medium being measured, they can be used in a wide range of applications, such as vacuum measurement, level measurement, or inventory level detection. Thanks to the use of advanced materials, it is resistant to extremely complex chemical and physical conditions, and it can provide accurate, reliable, and long-term stable analog or digital level signals. 　　5. Easy maintenance and simple operation The radar level gauge features fault alarm and self-diagnosis functions. Faults are analyzed based on the error codes indicated by the operation display module; the faults are identified promptly and resolved, thereby making maintenance and correction more convenient and accurate and ensuring the proper operation of the instruments. 　　6. Wide range of applications – it can measure almost all types of media. In terms of the shape of the tank, radar level gauges can be used to measure the level in spherical tanks, horizontal tanks, cylindrical tanks, and conical tanks ； In terms of tank functions, it is possible to measure the liquid level in storage tanks, buffer tanks, microwave tubes, and bypass pipes ； In terms of the medium to be measured, liquids, particles, slurries, etc., can be measured. 　　Summary: In general, radar level gauges have a wide range of applications and employ a non-contact measurement method. It features high-quality materials and a low failure rate. 　　Guided wave radar level gauge Principle: 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. When these pulses encounter the surface of the material, they are reflected back and captured by a receiver inside the instrument, which then converts the distance signal into a level signal. 　　Features: 1. Has a strong ability to suppress steam and foam, with no impact on measurements ； 　　2. Unaffected by liquid density, the looseness of solid materials, temperature, and dust during feeding ； 　　3. Low maintenance, high performance, high precision, high reliability, and long service life. 　　So is there any difference between them? 　　Different contact methods: Radar level gauges are non-contact, while waveguide level gauges are contact-type. In other words, pilot-type systems cannot be used in applications with high requirements for food grade. 　　The operating media are different: Guided wave radar level gauges require more consideration to be given to the corrosivity and stickiness of the medium, and installing and maintaining such gauges when they are too long is more difficult. 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. 　　The selection process differs: ordinary radars can be used interchangeably, whereas guided wave radars cannot generally 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. 　　Different measurement ranges: Conventional radars are commonly used for tanks with a diameter of 30 or 40 meters, and can even measure up to 60 meters. Guided wave radar also needs to take into account the stress on the guided wave rod (cable); due to this stress, the measurement range of guided wave radar is generally not very long. However, in some specific operating conditions, guided wave radar has clear advantages; for instance, when there is mixing inside the tank or significant fluctuations in the medium, the measurement values obtained using a guided wave radar fixed at the bottom are more stable than those from a movable radar ； 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, and this is where the advantages of guided wave radars become apparent.