Non-Contact Radar Level Sensor Working Principle

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

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. 

Here is the step-by-step process:

• 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.

Propagation of Radar Electromagnetic Waves

• Speed of electromagnetic waves is 300,000,000 m/s
• Influence of temperature, pressure and humidity can be neglected
• Conductive materials and materials with a different dielectric constant than air give reflections

Learn more about ABM’s non-contact radar level sensors here >