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Radar level gauges operate by using electromagnetic waves (commonly known as radar waves; they are called so because this ranging method was first applied in military radars). The working principle involves emitting electromagnetic waves at the target being measured; these waves are reflected back by the medium upon encountering it, and this reflection is used to determine the exact position of the liquid. For radar level gauges, the key function is to ensure that they can emit electromagnetic wave signals successfully. In industrial production environments, signal interference is a common issue. So, what are the sources of interference that affect the measurement of radar level gauges? For the signals of radar level gauges, there are many reasons for interference, and the sources of such interference are diverse. This article will discuss them from four aspects: internal, external, AC, and DC. 1. External interference 1. Interference from celestial bodies and atmospheric electrical phenomena. So, what exactly is interference from celestial bodies? Celestial bodies refer to the Sun or other stars; therefore, celestial interference means that the electromagnetic waves emitted by them cause certain disturbances to the signals sent by radar level gauges. Most people find atmospheric electricity quite unfamiliar. Generally, atmospheric electricity is understood as interference with the signals of radar level gauges caused by electromagnetic waves generated by ionization processes in the atmosphere or by lightning, or by natural phenomena such as volcanoes and earthquakes. 2. Mechanical interference: Mechanical interference refers to the situation in which severe vibrations or shocks from external machines affect the radar level gauge, causing certain components inside the gauge to vibrate, shift, or deform. This can also lead to the pointer of the gauge becoming loose, resulting in measurement errors. To address this issue, we typically use partitions and shock-absorbing springs to mitigate the impacts. 3. Humidity interference: As humidity increases, it leads to a decrease in the resistance of insulators, an increase in the dielectric constant of dielectrics, swelling of the framework, and an increase in resistance. This in turn results in an increase in leakage current, an increase in capacitance, and changes in inductance. It also softens the gel and reduces the measurement accuracy. 4. Chemical interference: Chemical interference generally refers to corrosive gases such as acids and alkalis. Prolonged exposure to these gases can not only damage instruments and their internal components, but also react with metals to conduct electricity, thereby affecting the normal operation of radar level gauges. 5. Thermal interference: During the operation of thermal power plants, their thermal equipment generates a large amount of heat, which in turn causes changes in the temperature of the surrounding instruments and the environment. This is what is referred to as thermal interference. Such interference can affect the components of radar level gauges, leading to issues such as inaccurate measurements. 6. Light interference: The issue of light interference relates primarily to semiconductor components. Many of the components used to control instruments are made of semiconductor materials, and when these semiconductor elements are exposed to light, their electrical conductivity changes. As a result, the proper operation of radar level gauges is affected. II. Internal interference: Interference does not come only from external sources; it can also arise from within the radar level gauge itself. For example, interference is generated by wires, power transformers, and inductance and capacitance values present between electronic components. In addition, the internal components themselves can produce noise interference. Today, most radar level gauges have also been improved by incorporating high-frequency microwave technology. This has **improved the performance of the level gauges, while reducing interference as well.** III. DC interference: In the measurement circuit of radar level gauges, the presence of an additional DC voltage constitutes DC interference. In severe cases, it will prevent the measuring instruments from functioning properly. The sources of DC interference include the following: (1) additional thermoelectric potential. (2) Chemical potential. (3) When the radar level gauge comes into contact with a DC power supply, the leakage current will generate an interference voltage in the measurement circuit. IV. AC interference: AC interference can be further divided into inter-wire interference and ground interference. Inter-wire interference refers to the occurrence of alternating voltage between the output terminals of a radar level gauge (compensation wires) as a result of external influences. This type of interference is also known as transverse, common-mode, or common-state interference. Under normal circumstances, the inter-wire interference voltage can reach several millivolts or even dozens of millivolts. Ground interference refers to the phenomenon that occurs at one of the two output terminals of a radar level gauge (or compensation wire), and the AC voltage with respect to ground at that terminal is known as the ground interference voltage. This type of interference is also known as longitudinal, intermodulation, or series interference. Under normal circumstances, the interference voltage relative to ground can reach several volts or even over 100 volts. The main sources of interference in AC systems are as follows: (1) Electromagnetic induction is the primary source of interference between wires. (2) Effects of high-temperature leakage. (3) High-voltage electric field interference. (4) Geoelectric current interference. (5) Effect of suction and leakage currents. (6) Temperature measurement on live conductors can also introduce AC interference. The above are the various situations we have discussed regarding interference with the signals of radar level gauges. When installing or using radar level gauges, we can use these factors to determine whether your operating environment might cause such interference. If such conditions exist, it is essential to take appropriate anti-interference measures to ensure that the level gauge can function properly for you.