Inductive loop system equivalent circuit model

The author describes the development and application of an equivalent circuit model and computer program to calculate the apparent self-inductance and quality factor vs. frequency of square, rectangular, quadrupole, and circular loops of round wire buried in a roadway. The computer program calculates the loop apparent inductance and quality factor versus operating frequency (20-60 kHz) for a selected loop size, shape, conductor size, number of turns, turn spacing, slot width, pavement loss tangent, and slot-sealant-material dielectric constant. The effect of transmission lines and matching transformers between the loop in the roadway and roadside vehicle detector electronics is included in the model. The capacitance between the loop conductors and surrounding pavement material is shown to have a major effect on the magnitude of the loop´s apparent self inductance