In chemical production, it is often necessary to detect the separation surface of different media, commonly known as the interface level, to meet the requirements of process production. Depending on the actual on-site working conditions, the mainstream solutions for interface level measurement include those based on density differences and those based on dielectric constant differences. The instruments commonly used for interface level measurement are differential pressure level gauges, float level gauges, magnetostrictive level gauges, guided wave radar level gauges, and so on.
If the density difference between the two measured media is small, the differential pressure method or float-type measurement cannot be applied. In such cases, if the dielectric constant difference between the two media is significant, the measurement based on dielectric constant difference can be considered. Guided wave radar level gauges are widely adopted for this measurement method in industrial production.
The measurement principle of a guided wave radar level gauge is that radar waves are transmitted and reflected as echoes when they encounter the separation surface. After the receiving sensor captures the echoes, the distance, i.e., the interface level, is calculated based on the TOF (Time of Flight) principle using the wave speed. When using a guided wave radar level gauge to measure the interface, it is essential to ensure that the light medium has a poor reflection effect on radar waves, which means a large dielectric constant difference between the two media—popularly speaking, one is an insulator and the other is a good conductor.
Compared with other interface level measurement solutions, the main advantages of guided wave radar level gauges lie in that radar signals propagate along the guided wave rod, with concentrated transmission and reflection energy and almost no attenuation. This characteristic enables the guided wave radar level gauge to produce strong reflected signals, and the measurement accuracy is not affected by various external factors, nor does the measurement result change with variations in temperature, pressure and medium physical properties, thus ensuring measurement accuracy.
However, guided wave radar also has certain limitations that need to be noted: the principle of radar level gauges requires that the upper medium has a smaller dielectric constant and the lower medium has a larger one at the separation surface, and the larger the dielectric constant difference, the better. If the two media are stratified but their dielectric constant difference is small, accurate measurement cannot be achieved. In addition, complex conditions such as a large amount of suspension and emulsification at the separation surface, or working conditions that generate foam and water vapor, may also affect the measurement accuracy. Meanwhile, attention should be paid to the installation position of the radar level gauge during installation; it should be kept away from feed inlets, agitators and other positions. Improper installation will cause interference to the echo signals of radar waves. Therefore, during installation, the height of the storage tank and the distance between the installation position and the tank wall need to be considered, and sufficient installation space should be reserved for the radar level gauge.
In some relatively complex measurement environments, the obstacles encountered by microwaves during propagation are not just the materials, which will generate multiple echoes and ultimately lead to the failure to accurately determine the material position. To address the above situation, special measures are required. The installation of a guided wave tube or a bypass channel can effectively solve such problems.
The installation of a guided wave tube or a bypass channel can effectively avoid the interference of obstacles on measurement. Of course, this is only applicable to certain specific actual working conditions, because only media with good fluidity can ensure that the guided wave tube or bypass channel is at the same horizontal level as the main measured container, and it is not suitable for viscous media. It is also worth noting that the inner wall of the guided wave tube or bypass channel must be smooth to ensure that the fluidity of the medium is not disturbed, so as not to affect the measurement. In addition, the height requirement for the connecting pipe is that the antenna must extend into the tank by at least 10 mm.
Contact Information
Website: https://www.radar-leveltransmitter.com/
Email: sales@nuoying-instru.com
Phone: +86 18210049286
