Using Signal-to-Noise Ratio as Evidence to Detect Presence-Absence of Vehicles

摘要

There are three different loop detectors used to detect present and absent vehicles. One of them is known as self-tuning detector. This type of detector utilizes both pavement loops as part of a parallel resonant tank circuit and a closed-loop feedback circuit. It automatically adjusts a voltage-tuned oscillator to a predetermined frequency relative to the resonant frequency of the tank. A change in the loop inductance shifts the resonant frequency of the tank, which results in a change in the feedback voltage.