What is a Radar Level Sensor? Working Principle Explained

What is a Radar Level Sensor? Working Principle Explained

What is a Radar Level Sensor?

A radar level sensor is a device that uses radar technology to measure the level of a substance, such as a liquid or solid, in a container, tank, silo or bin. It is a continuous level measurement device that provides real-time, non-contact level monitoring.

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How Does a Radar Level Sensor Work?

The basic working principle involves transmitting a burst of electromagnetic waves (microwaves) from the sensor and measuring the time it takes for the waves to travel to the target and back. The time-of-flight is then used to calculate the distance. 

Step-by-Step Operating Principle

• A radar electromagnetic burst is transmitted and directed by a dielectric rod antenna or metal horn antenna.
• The electromagnetic waves (microwaves) propagate toward the surface of the target and then reflect back towards the sensor.
• The reflected waves are received by the same antenna and converted to an electrical signal.
• The electrical signal is amplified and processed.
• The sensor measures the time it takes for the emitted waves to travel to the material surface and back using time-of-flight principle.
• The microprocessor in the sensor calculates the distance to the target using the speed of light, a known variable, and the round-trip time as shown in the following equation:
  • Distance = Time x Speed / 2
  • Where division by two is required as time measurement is round-trip (to the target and back)
• The calculated distance is converted linearly to 4 mA to 20 mA current. Optionally, information can be sent via RS232 or RS485 to a PC for processing such as diagnostics, programmable set-up and data logging.
• The distance measurement is then used to determine the level of the substance in the tank.

When to use Radar Level Sensors

Radar level sensors are ideal for continuous level measurement of liquids and solids in challenging environments that have vapour, gases, temperature variations, extreme temperatures, extreme dust, wind, foam, ice or acoustic noise. 

Propagation of Electromagnetic Waves

• Microwaves do not need a medium to travel, they can travel in a vacuum
• Speed of electromagnetic waves is 300,000,000 m/s
• Electromagnetic waves are not effected by temperature, pressure or humidity
• The reflection depends on the dielectric constant of the liquid or solid material
• The higher the dielectric constant, the better the reflection. As an example, water has a dielectric contact of ~80 where as plastic pellets have a dielectric constant of ~1.5

Types of Radar Level Sensors

There are several types of non-contact radar level sensors available, each suited to different applications, environments or the material being measured.

The radar level transmitters are widely used for level measurements in different applications. There are two types of radar level transmitters – non-contact systems and contact systems. Before making a buying decision, it is important to understand these systems and their underlying technologies in detail. The setup and working principle of Radar Level Transmitters were discussed in detail in the previous post. This final part of the two-part post gives insights about radar transmitter functioning technologies and its industrial significance in terms of applications.

Know About Different Types of Technologies in Radar Level Transmitters

Radar level transmitters may be powered by any of these technologies:

Guided Wave Radar Level Transmitter:

In this guided wave radar technology, the guided radar probes are utilized. It is a contact or invasive type of transmitter, where Time Domain Reflectometry (TDR) probes are immersed in dry or bulk media. These probes can detect the advancing motion of the electromagnetic waves. TDR probe gets rid of any obstacles in between the path of waves, therefore the loss of signal is not a concern in this type of technology. Guided TDR probes are highly immune to high temperatures, pressure, and environmental damage, therefore this technology is suitable for harsh operational environments. This technology is highly compatible with high-end industrial applications because it needs almost zero maintenance. This technology is used in the guided wave radar level sensors and guided wave radar level transmitters.

Frequency Modulated Continuous Wave (FMCW) Transmitters:

The radar transmitters working on FMCW technology make use of radar antenna. The radar antenna emits a signal and the receiver catches it within a specific time. This time reading is considered during level measurements. FMCW radar emits high-frequency continuous signals with gradually increasing frequency. It is called frequency sweep and due to this, continuous measurement is possible in this technology. These are basically a non-contact type of level transmitters.

Ultrasonic Level Transmitters: In ultrasonic level measurement, sound waves are transmitted to the fluid surface. The speed of sound travel and reflection is converted to distance traveled, which is the level of fluid surface. This technology uses air medium, therefore it is not suitable for vacuum level measurement. This is also a non-contact type of level transmitter.

Owing to the variation in technologies, and versatile functions, these radar transmitters are highly significant in various industries. The significance of these level transmitters is discussed as applications.

If you are looking for more details, kindly visit radar type level transmitter.

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Where are these Radar Level Transmitters Used?

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The radar level transmitters being accurate are used in critical engineering environments. The industrial applications of these transmitters or level sensors are as follows.

Mining Industry:

In the mining industry, these transmitters are used to check the depth or length of mines or to check the level of the surface of the ore. Generally, FMCW radar level transmitters are used here due to frequency continuity. Sometimes if only air medium is available then ultrasonic radar technology may be used.

Boiler Engineering:

Boilers are hazardous equipment. It is very difficult to measure fluid level due to extremely high water and stream temperature. In such cases guided wave radar level sensors are used. These guided probes are immune to high temperatures. Therefore, they are used in boiler technologies as fuel level or fluid level indicators.

Aeronautics Industry:

In automobile industries, the fuel levels are often tested by using contact type level indicators. However, in aeronautics, a fuel storage system is a little complex. Therefore, radar level transmitters are used.

Paper and Pulp Industry:

In the paper and pulp industry, in order to measure the level of slurry, water and storage tanks, these level transmitters are used. Guided probes can be used in the chemical atmospheres, therefore it is a suitable choice in paper and pulp industry.

Bore Digging Technology:

In the bore digging process, the devices are exposed to mud, slurry, and under surface gases. In such cases, these level indicators are used to check to dig surface levels.

Now, that the working principle and functioning technologies are persuaded, it is important to source these devices from trusted suppliers. Leading manufacturers like Emerson offer Rosemount radar level measurement sensors in different configurations. It is important to buy from a supplier who is associated with prominent brands. The Transmitter Shop is a company that has been supplying branded quality transmitters since . They provide new, reconditioned, and surplus transmitters from Rosemount, Foxboro, Honeywell, and many more.

Contact us to discuss your requirements of pressure level transducer. Our experienced sales team can help you identify the options that best suit your needs.

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