AVI and No Visible Reader
May, 2007
Juliene Larsen
Security and routine operations at most plants and refineries are often at cross purposes. Efficiency demands that workers have quick access to all areas of the facility whenever necessary. However, leaving gates and other entrances unguarded is simply not an option in post-9/11 America.
Now, technology familiar to most Americans has been adapted into a security issue solution. Inductive loop vehicle detection technology was developed in the 1960s as a means of acquiring vehicle presence and count information needed to vary the timing of traffic signals.
Such a system consists of two parts: an in-pavement inductive loop and a detector module. An inductive loop is a wire usually wound in a rectangular, square or round shape installed in the pavement. The ends of the wire are brought back to an enclosure that houses the detector module. An oscillator circuit in the detector module powers the loop.
The electrical current flowing in the loop creates a magnetic field. When a vehicle’s metal enters the magnetic field of the loop, a loading effect occurs, which changes the loop frequency. The detector module monitors the loop frequency, and when a sufficient frequency change occurs, the detector produces an output signal.
Today, ILV systems remain the most accurate and reliable method for detecting vehicles, said Thomas R. Potter, President of Reno A&E.
“In addition to conventional vehicle detectors, the industry has developed an automatic vehicle identification (AVI) system using in-pavement inductive loops,” Potter said. “It incorporates a vehicle-mounted transmitter that generates a low-frequency, digitally encoded signal.
“The transmitter is powered from the vehicle’s electrical
system, and depending on the application, can be operated either continuously or controlled by application of power to the transmitter. The digitally encoded signal is coupled through an in-pavement inductive loop to a compatible AVI receiver.
“Since the signal is low frequency and inductively coupled, the vehicle-mounted transmitter must be directly over the in-pavement inductive loop in order to be recognized. When a coded signal, which has been authorized, is recognized by the AVI receiver, a signal is output to a controller used for controlling the movement of a gate or overhead door.
“Unless the code is authorized, access is denied to the vehicle,” Potter said. “This adds a new layer of security for the most sensitive areas of the facility.”
The AVI system has been operating reliably for fire departments in the Las Vegas Valley for more than 15 years. The same technology is used in Los Angeles for the rapid bus system, which tracks rapid buses through intersections and, if needed, can modify signal timing to keep them on schedule.
The parking industry can use this AVI technology to monitor and/or control movement of vehicles. In addition to the authorization of codes, which grants or denies vehicle access, the Windows-based system software is capable of logging and time-stamping all AVI-equipped vehicles entering and exiting through gates equipped with appropriate AVI receivers.
The AVI system is designed to provide an excellent, reliable, and trouble-free method of identifying specific vehicles. “Applications are limited only by one’s imagination,” Potter said.
In post 9/11 America, when it’s crucial to control plant and remote-facility access with limited manpower, this technology can be your best friend.
Juliene Larsen is marketing administrator for Reno A&E. She can be reached at julienel@renoae.com.
