Radar Level Transmitter

Overview

A radar level transmitter measures the vertical distance to a liquid surface or solid pile by transmitting microwave electromagnetic pulses downward and detecting reflections from the material surface. The transmitter's microcontroller calculates level by measuring echo time-of-flight: distance = (speed of light × time) / 2. Radar works in virtually any tank or silo, regardless of dust, vapor, foam, or temperature, because microwaves penetrate most industrial atmospheres that would blind ultrasonic or optical sensors. Typical accuracy is ±20–50 mm over 10–30 m range, suitable for tank inventory, water treatment, and blast furnace burden profile.

The system centers on a Microwave Module generating 24 GHz (or 5.8 GHz) pulses and receiving echoes, a Signal Processor computing level via time-of-flight, and a Antenna Assembly radiating the beam downward. The Antenna Support holds the antenna above the tank surface (standoff distance), and the Display Head provides local feedback.

How it works

The Voltage-Controlled Oscillator generates a continuous 24 GHz carrier modulated with a brief pulse envelope. The Power Amplifier boosts the signal to 100 mW and launches it down the Antenna Assembly. Microwaves travel at approximately 3 × 10⁸ m/s (adjusted for the dielectric constant of air and vapor above the material) and reflect off the material surface.

The return echo arrives at the antenna, is routed by the Directional Coupler to the receiver, and down-converted by the Receiver Mixer to a lower intermediate frequency. The Analog-to-Digital Converter samples the echo waveform at 1–10 GHz, and the Microcontroller executes time-of-flight edge detection: it finds the rising edge of the echo and calculates the round-trip time Δt. Level = (c × Δt) / 2, where c is the speed of light adjusted for vessel atmosphere. Calibration accounts for antenna standoff, tank height reference, and material-specific reflectivity.

Radar excels in dusty or foamy environments because the 24 GHz wavelength (≈12 mm) reflects off large particles and liquid foam but penetrates light dust and steam. Low-frequency (5.8 GHz) variants have longer range but lower accuracy; high-frequency (77 GHz) variants offer finer resolution but shorter range. Multiple echo peaks (false echoes from tank walls, agitators, or internal fixtures) are rejected by the software recognizing the strongest, lowest-altitude echo as the true surface.