Monitor differentiating between cars and goods vehicles - uses two inductive loops in road driving constant voltage and current sources via relays

摘要

A method of monitoring road traffic differentiates between cars and goods vehicles by monitoring the changing inductance of loops in the road as the vehicle passes over them. The different vehicle classes are distinguished, almost regardless of their lengths. The inductive change observed in a suitable inductive loop beneath the travelling vehicle depends on the floor height, as well as the vehicle length, to give a contour characteristic of the vehicle type. - The equipment uses two loops which drive a number of constant voltage and constant current sources via relays and a storage capacitance in such a way that three counters, clocked during the relay on times indicate the type of vehicle that has passed.