Most inductive loops are formed by wrapping a single wire strand around the loop shape a prescribed number of times. Because these turns are spaced randomly, the electromagenetic field, and consequently detection results may vary from detector to detector. It has been established that a multiconductor cable, which holds the loops in uniform proximity, will produce more accurate measurements. Installation of the multiconductor necessitates a wider cut into the pavement than the single wire configuration. Ruggedized, weather resistant pre-formed loops are available which aid in uniformity, but also can be more difficult to install.
Detectors operate in either the pulse or presence mode.
Many detectors today employ digital technologies which sense a change in the resonant frequency of a loop due to a decrease in inductance. Digital techniques allow more reliable and precise measurements than their analog counterparts. These features can significantly reduce detector maintenance costs and calls. A consistent and fast response time is crucial for accurate speed measurements. Response time is affected by vehicle size, speed, detector type, sensitivity, and wire type.