For inductive loops at traffic lights to detect cars, must the cars conduct electricity or a magnetic field?
The car must have at least some parts that can be magnetized, like iron or steel. I doubt if an all Aluminum car would be detectable. Certainly an all plastic car would not be detectable. I'm not sure how much magnetic material a car has to have for the road inductor to sense it. Probably all that's needed is a steel motor block. Some of these all electric cars might not have enough steel to be detected. Basically its like sticking an iron bar inside, or near, a coil. The inductance changes dramatically because the the magnetic field of the coil induces a magnetic field in the bar which adds to the coils field , and that can be measured.
some site visitors systems do use an common rigidity plate to sense some thing on the pavement above. it rather is an older technologies it rather is customarily being replaced with the inductive loop, it rather is one among those electromagnetic field created by utilising a device buried under the line. think of a tire floating vertically in a lake. you in basic terms see the proper a million/2 of it. replace capability for the tire, and pavement for the lake, and that's what it appears like. in basic terms this field could be over 10 feet long. invisible, barrel-mendacity-on-its-area-formed capability field. the proper a million/2 of the tire is above the pavement. while an merchandise drives on proper of this device, it disrupts the electromagnetic field interior the air above the line. If the disturbance meets a definite era and quantity, i.e. automobile-sized or greater effective, for longer than 2 seconds, a command is despatched to the sunshine controller. super or busy intersections on occasion use multiple inductive loop sensors in one lane so they are able to offer priority to which highway at present has the heaviest backup. Metro aspects use this, in tandem with a distant administration pc equipment, so they are able to alter gentle intervals at specific situations of day, or days of the week, or supply priority to larger roads, if site visitors controllers observe intense backups or delays forming.
