User's Manual

Versus Technology, Inc.
14 Versus Information System
3.3.1 Sensor Connection Length Limitations
The sensor wire runs can be up to 1000 feet in length from the Collector to the sensor. If the
environment is known to be electrically “noisy,” consider shorter line lengths for stronger signals
and immunity to interference.
3.3.2 Infrared (IR) Sensor Location Planning
Several factors will determine where you install IR sensors, including the sensors’ field-of-view,
effective or overlapping coverage, and possible interference from sunlight, plasma screens,
lighting and EMI noise.
3.3.2.1 IR Sensor “field-of-view”
If an IR sensor is placed in a room with obstacles and reflections eliminated, the field of view
of the sensor appears in the shape of six overlapping lobes forming a 15-foot radius.
The 30-foot diameter cone of coverage was determined based on the sensor being placed in
an 8 foot ceiling and the badge being approximately 4.5 feet off the ground.
An IR sensor “sees” the environment under it in a largely predictable pattern. However, there
are factors that can affect this field of view. The sensor is like an eye, which is sensitive only
to a narrow spectrum of light, and the signals from a badge appear as a bright splash in an
otherwise dark world to the sensor. Even if the badge is blocked from the view of a sensor, it
can often be detected. The infrared light from a badge does not penetrate solid objects or bend
around corners, but it does reflect off surfaces. This can sometimes be mistaken for “seeing
around corners.” The effect of reflection can be used to advantage by the system designer, but
can also pose problems if the installer is unaware of it. Sensors have a given field of view
when obstacles are not present, but the field of view of an installed sensor will vary due to
room configurations.
A sensor may have a field of view that extends out of the designated area through a doorway
or passage. This can cause badges to be detected incorrectly and reported to be in the room
when only passing by. Place sensors near the middle of rooms, but offset from doors or
entryways to prevent false detection. The position of a sensor can limit its view by placing it
in a location where existing obstacles will block any unwanted sensor view.