How do radar level transmitters work?

Radar level gauge working principle

The radar level gauge uses ultra-high frequency electromagnetic waves to transmit to the liquid level of the detected container through the antenna. When the electromagnetic waves are reflected back after hitting the liquid level, the instrument detects the time difference between the transmitted waves and the echoes, thereby calculating the height of the liquid level. The better the conductivity of the measured medium or the greater the dielectric constant, the better the reflection effect of the echo signal.

Radar level gauge is mainly composed of transmitting and receiving device, signal processor, antenna, operation panel, display and other parts. Transmit-reflect-receive is the basic principle of radar level gauge work. It is divided into time difference type and frequency difference type.

The time difference type is that the transmission frequency is fixed. By measuring the running time of the transmitted wave and the reflected wave, and through an intelligent signal processor, the height of the measured liquid level is measured. The relationship between the running time of this type of radar level gauge and the liquid level distance is: t=2d/c. 

In the formula, C is the propagation speed of electromagnetic wave, c=300000km/s; d is the distance between the liquid level of the measured medium and the probe, m; t is the time from the launch of the electromagnetic wave to the reception of the reflected electromagnetic wave by the probe, s.

The frequency difference type measures the frequency difference between the transmitted wave and the reflected wave, and converts the frequency difference into an electrical signal proportional to the measured liquid level. The emission frequency of this type of liquid level gauge is not a fixed frequency, but an adjustable frequency of equal amplitude.

Radar level meter features and main performance parameters

The radar level gauge shows its performance even under harsh measurement conditions such as flammable, explosive, highly corrosive, high temperature, and viscosity, and is especially suitable for the measurement of large vertical tanks and spherical tanks. The performance of liquid level gauges of different manufacturers is different, please refer to the relevant information of the manufacturers for details. The understanding of its performance is conducive to the correct use of the radar level gauge.

Selection of radar level measurement

The antenna is the key component of the radar level gauge, and the shape of the antenna determines the focus and sensitivity of the radar wave.

The horn antenna is suitable for most occasions, and the focusing characteristics are particularly good. Many storage tanks in the field use this type of antenna, but it is not suitable for the measurement of corrosive media.

The mounting flange of the rod antenna is small in size, has good chemical stability, is easy to clean, and is not sensitive to the adhesion of condensed water. It is especially suitable for measuring corrosive media (such as sulfur) and for high-precision measurement in narrow installation short pipes. .

The under-flange antenna is suitable for high temperature media, corrosive media or environments where top installation is not possible.

The parabolic antenna has good focusing and is not affected by heating steam, especially suitable for in-tank measurement of large containers with heating steam, such as the measurement of residual oil, asphalt, etc., the measurement range can reach 40m

Radar transmitters application

Oil tank farms are important storage and transportation facilities in petrochemical enterprises. Accurately measuring the inventory of oil tank farms plays a very important role in guiding the production and sales of petrochemical enterprises. As a key instrument in the measurement of oil tank farms, tanks. The accuracy, safety and stability of the regional level gauge directly affect the safety production and economic benefits of petrochemical enterprises. 

As early as the mid-1980s, radar measurement technology from the military industry was applied to the field of industrial automation measurement, which made a fundamental leap in modern tank field measurement technology and solved the problem of oil tank field measurement systems in some working conditions. For a long time, the difficulty of accurate measurement has been difficult, and the radar level gauge has become the first choice for the liquid level measuring instrument in the tank area due to its superior performance.

As an intelligent liquid level measuring instrument, the radar level gauge has already exerted its own unique advantages in the application of oil measurement in the tank area. The advantages of non-contact measurement, large measurement range, high precision, and simple installation are completely To meet the requirements for accuracy, reliability and stability of oil measurement in the tank area, the digital fieldbus transmission method can not only save costs, but also meet the requirements of modern measurement technology developing towards integration, digitization and networking. Meters will continue to play an important role in tank farm oil metering.