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 measurement.

Radar Level Sensor Working Principle

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.