Through testing an elevation of 24 inches has proven to be the most reliable for detection of all makes and models of vehicles. The minimum detection range of the sensor is 12 inches. The sensor must be located so a vehicle cannot come closer than this distance or the vehicle may not be detected. The sensor must be mounted so that it is perpendicular to the vehicle. If the vehicle is aligned at an angle to the sensor the sound will be reflected away, causing the sensor to indicate no vehicle is present.
Acceptable alignment is between zero and five degrees off perpendicular.
The IRU-1002 used for presence detection at the terminal has two adjustments, sensitivity and trip distance. They are set via single turn potentiometers. A vehicle presents a good reflective target for the sound wave, and the detection distance is less than four feet. A high sensitivity level would leave the sensor susceptible to false triggering if high levels of street noise are present. The second adjustment is the trip distance.