Principle Analysis and Accuracy Calculation of Radar Liquid Level Meter

The antenna of the radar sensor emits electromagnetic wave signals in the form of beams. The emitted waves are reflected on the surface of the material to be measured, and the reflected echo signals are still received by the antenna. Every point in the transmitted and reflected beams is collected by ultrasonic sampling. After the signal is processed by the intelligent processor, the distance between the medium and the probe is obtained and sent to the terminal display for display, alarm, and operation. During the transmission time interval, the antenna system is used as a receiving device. The instrument analyzes and processes the echo signal whose running time is less than one billionth of a second, and analyzes and processes the echo in a very short moment.

The radar sensor uses a special time interval adjustment technology to amplify and locate the echo signals per second, and then analyze and process them. Therefore, the radar sensor can analyze and process these amplified echo signals accurately and meticulously within 0.1s, without spending a lot of time analyzing the frequency.

The strength of the reflected signal is highly dependent on the dielectric constant of the fluid. Water (ε = 80) is much easier to measure than hydrocarbons (ε <25). The sensors can be tuned to measure either, however.

Two operating principles are used: time of flight (TOF) and frequency modulated continuous wave (FMCW). Modern instruments have overcome deficiencies that once plagued the FMCW technology. Select the device on the basis of its accuracy, beam angle, and antenna diameter rather than on the type of radar signalling.

The absolute accuracy of a radar detector is improved with a higher signal frequency which is generally 6, 26, or 80 GHz. The accuracy is typically
6-10 mm at 6 GHz and <1 mm at 80 GHz. But the service accuracy is also affected by the nature of the surface of the fluid in the tank. The beam angle decreases with increased frequency. If the surface of the fluid is choppy or wavy, a wider angle might do a better job of smoothing out the signal. This is somewhat analogous to an auto-focus camera that can be set to focus on a tight spot or on the average of the wider scene; the spot will be correctly focused while another subject in the photo is blurry. However, algorithms in modern electronics can mitigate this effect and allow for the use of high frequency signals even with very turbulent surfaces.

Beam angle is an important consideration when deciding where to locate the transmitter on the tank head. You want the beam to avoid hitting the tank wall because that will disrupt the reflected signal and decrease the strength and robustness of the measurement. Radar sensors are fitted with an antenna; the diameter and shape of the antenna, in addition to the signal frequency, determine the beam angle. Many radar units can be programmed to [map out" signals that are reflected from internals in the tank, including the wall, but it is still better practice to keep them out of the beam