The working principle of radar level gauges and their applications

A radar level gauge emits its own pulse wave, which is reflected back when it hits the surface being measured. The liquid level is determined based on the time taken for the pulse to be sent and the reflected wave to be received. As for the type of container, I think it should be one with a slightly larger diameter, because if the diameter is small, the pulse waves will hit the container walls and reflect back, affecting the measurements. Generally, for containers where ultrasonic level gauges can be used, we don’t need radar level gauges, as they are cheaper.

Radar level gauges emit extremely low-power, short microwave pulses through an antenna system for transmission and reception. Radar waves travel at the speed of light. Operating time can be converted into a level signal through electronic components. A special time extension method can ensure stable and accurate measurements in an extremely short period of time. Even in complex operating conditions with false echoes present, the latest microprocessing technology and debugging software can still accurately analyze the echoes corresponding to the liquid level. The antenna receives the reflected microwave pulses and transmits them to the electronic circuitry; the microprocessor processes these signals to identify the echoes generated by the micropulses on the surface of the material. The accurate identification of echo signals is carried out by intelligent software, with precision reaching the millimeter level. The distance D from the surface of the material is proportional to the time duration T of the pulse: D = C×T/2, where C is the speed of light. Since the distance E of the empty tank is known, the material level L can be calculated as follows: L = E – D. The output is determined by specifying the height of the empty tank E (which corresponds to the zero point), the height of the full tank F (which corresponds to the full scale), as well as some application parameters; these parameters enable the instrument to adapt itself to the measurement conditions. Corresponds to a 4‑20mA output. Application media:  The SKD series of intelligent radar level gauges are suitable for non-contact, continuous measurement of the level of liquids, slurries, and granular materials, and can handle large variations in temperature and pressure ； In situations where inert gases and vapors are present.  It employs a microwave pulse measurement method and can operate properly within the industrial frequency band. It has a low beam energy, can be installed in various metal and non-metal containers or pipes, and causes no harm to humans or the environment. Installation instructions  Recommended distance (1) from the wall to the outer wall of the installation stub:  It should be at 1/6 of the tank’s diameter from the tank wall, with a minimum distance of 200 mm.  It cannot be installed above the feed inlet (4).  It cannot be installed in the center position (3); if installed there, multiple false echoes will be generated, and these interfering echoes can cause the signal to be lost.  If the distance between the instrument and the tank wall cannot be maintained, the medium on the tank wall will adhere, causing false echoes; false echoes should be stored during instrument calibration. Measurement conditions and precautions  The measurement range starts from the point where the beam touches the bottom of the tank; however, in special cases where the bottom of the tank is concave or conical, measurement cannot be carried out when the liquid level is below this point.  When the dielectric constant of the medium is low and the liquid level is low, the bottom of the tank becomes visible; to ensure measurement accuracy, it is recommended to set the zero point at a height of C.  Theoretically, it is possible to measure the position at the tip of the antenna, but considering the effects of corrosion and adhesion, the end value of the measurement range should be at least 100 mm away from the tip of the antenna.  For overflow protection, a safety distance can be defined and added to the blind area.  The minimum measurement range is related to the antenna.  Depending on the concentration, foam can either absorb microwaves or reflect them, but it is possible to make measurements under certain conditions.

Radar level gauges transmit and receive extremely short microwave pulses with very low energy via an antenna system. Radar waves travel at the speed of light. Operating time can be converted into a level signal via electronic components. Measurement range: The measurement range starts from the point where the beam touches the bottom of the tank; however, in special cases where the bottom of the tank is concave or conical, measurement is not possible when the liquid level is below this point. 

A radar level gauge is a device that sends microwaves toward the liquid level of the medium being measured via an antenna, and then determines the liquid level inside the container by measuring the time it takes for the microwaves to return. The characteristics of radar level gauges are as follows: no displacement, no moving parts, and contactless measurement. They are not affected by temperature, pressure, steam, mist, or dust, and are suitable for measuring the level of media with high viscosity, toxic or non-toxic sanitary media, as well as corrosive media. Radar level gauges have no measurement blind spots, and their accuracy (resolution) can be very high; the maximum error in level measurement is 1 mm (and 0.1 mm in special cases), making them suitable as commercial measuring instruments. When installing a radar level gauge, it should be placed away from the feed inlet, feed curtain, and vortices, as the liquid injected there generates spurious echoes with amplitudes much greater than those of the effective echoes reflected by the liquid level being measured. At the same time, the irregular liquid level caused by the vortex scatters the microwave signals, resulting in a attenuation of the effective signal; however, the effective signal can still be measured. For containers equipped with agitators, the radar level gauge should not be installed near the agitator, as the stirring action creates irregular vortices that can cause attenuation of the radar signal. At the same time, the blades of the stirrer can also generate false echoes for the microwave signal; this effect is particularly severe when the relative permittivity of the object being measured is low and the liquid level is low.

In simple terms, the principle of a radar level (material level) gauge involves emitting microwaves toward the liquid surface or object surface, and then receiving them; the time difference or frequency difference between these waves is analyzed. The former type is pulse radar, while the latter is FMCW (Frequency-Modulated Continuous Wave) radar

Ignoring costs, radar level gauges are practically suitable for use anywhere these days. Radar is contactless and has no moving parts; it offers advantages in measuring solids, highly viscous liquids, and liquid levels. Large-range measurement can reduce costs.

Points to note when installing a radar level gauge: 1. When installing a radar level gauge, it is necessary to avoid the feed inlet, feed curtain, and vortices, as the liquid flowing in generates false echoes with amplitudes much greater than those of the effective echoes reflected by the liquid level being measured. At the same time, the irregular liquid levels caused by vortices scatter microwave signals, leading to a reduction in the intensity of the effective signals; therefore, such vortices should be avoided ； 　　2. For containers equipped with agitators, the radar level gauge should not be installed near the agitator, as the stirring action creates irregular vortices that can cause attenuation of the radar signal. At the same time, the blades of the stirrer can also generate false echoes for the microwave signals; this effect is particularly severe when the relative dielectric constant of the object being measured is low or when the liquid level is low ； 　　3. When radar level gauges are used to measure the level of corrosive or crystalline substances, in order to prevent the medium from affecting the sensor, manufacturers generally employ a design with a polytetrafluoroethylene measurement window and a separated flange structure. The temperature of these components cannot be too high; the maximum temperature for polytetrafluoroethylene is 200°C. To avoid the effects of high temperatures on the radar antenna, and to prevent crystals present on the diaphragm from interfering with the proper operation of the instrument, it is required that there be a safety distance of at least 100–800 mm between the flange face and the highest liquid level