loopsensorer

Loop sensors, or loopsensorer, are electrical sensing devices that detect the presence or position of metal objects within or near a loop of conductor. They operate on the principle of inductive coupling: an alternating current through the loop creates a magnetic field, and when a metal object enters or near the loop, the object alters the loop’s inductance and impedance. A connected controller monitors these changes to determine presence, count, or movement. The sensing element is typically a rectangular loop of copper wire embedded in a surface such as asphalt, concrete, or floor.

Installations usually involve placing the loop in a groove or trench, sealing it with an epoxy or protective cover, and routing cables to a detector or controller. Loop sensors are widely used because the sensing element is passive and robust, with the detection hardware located remotely from the loop itself. They are common in traffic systems and security setups, but are also found in industrial automation where metal presence or positioning needs to be detected.

Common applications include vehicle detection at intersections and toll booths, parking guidance and gate control, railway platform monitoring, and various manufacturing or material handling systems. Variants may employ single or multiple loops to capture different vehicle sizes or movement patterns. Advanced detectors can infer speed or length by analyzing the activation pattern of sequential loops.

Advantages include durability in harsh environments and compatibility with various control systems. Limitations involve installation complexity, especially in resurfacing projects; sensitivity to nearby ferromagnetic materials; and potential misdetection from non-vehicle metal objects. Ongoing use often involves integration with complementary sensors or transition to alternative detection technologies where appropriate.