Principle of operation

The RTG employs the Frequency Modulated Continuous Wave

(FMCW) principle with dual sweep technology to eliminate

Doppler-effect caused by cargo movement. Frequency sweep

ing microwave signals are emitted from two separate electronic

units and through a common standpipe. The distance (i.e. the

ullage) is derived from the time delay of the reflected signal.

The standpipe is assembled by sections adjusted to match the

total tank height. The pipes have ventilation holes allowing the

vapour pressure inside and outside the pipe to stabilize, thus

allowing the liquid to rise or fall unimpeded in the pipe.

Each pipe section is supplied with flanges prepared with refer

ence markers. The liquid level and the markers are measured

simultaneously, so the system automatically verifies itself at

every measurement. By careful calibration of the pipe sections

length before installation, the positions of the markers are re

corded and stored in the system. By comparing the liquid echo

with the signature plate echo, a continuous auto-calibration of

the measurement is done.

The electronic units in the RTG includes a patented signal

detection method that ensures optimum performance. Com

bined with its superb signal-to-noise ratio, GLA-310/5 offers the

highest measurement reliability and accuracy.

Each electronic unit is connected to a dedicated signal process

ing unit, where the AutroCAL® principle is employed.