User's Manual

Versus Technology, Inc.
Hardware and Wiring Installation Guide 17
pulses produced by the badge.
Large plasma computer displays (such as the NEC 42MP2) emit large quantities of IR,
including IR light in the 880-nanometer wavelength. Like visible light, these inadvertent
emissions bounce off any reflective surfaces such as walls, floors, doors, etc., effectively
“flooding” the immediate area with 880-nanometer IR light.
Much like attempting to read white print on white paper, distinguishing the low-power IR
light of the VIS badge from intense background IR light becomes impossible in such an
environment.
Versus recommends that IR sensors not be installed in proximity to plasma screens. Because
the emissions vary greatly depending on the size and manufacturer of these displays, Versus
recommends allowing excess sensor wire and then testing the effectiveness of any sensors to
be installed near one of these displays prior to permanently mounting the sensor in the ceiling.
3.3.2.7 IR Sensor Interference From Nearby Lighting or EMI Noise
System performance can be adversely affected by;
1. Light that is aimed directly into the sensor.
2. EMI noise emitted by nearby electrical fixtures.
3. Light fixtures that hang below the sensor and shine directly up into the sensor.
Symptoms of sensor interference are:
1. A voltage drop below 15.5 volts.
2. Badges that are not picked up by the sensor or only picked up intermittently.
Do not mount sensors near lights or electrical fixtures unless absolutely necessary. If the
performance of an IR sensor is in question, move the sensor as far away from any nearby
lights or electrical fixtures as is practical. If the light fixtures are causing problems, try
mounting the sensors off the ends of the fixtures if you can’t move them fair enough away.
To avoid problems with light interference:
If sensors must be mounted near lights;
1. Mount sensor as far from the light as possible
2. Mount sensor so that the light does not have a direct path into the sensor “eyes.”
3. As a last resort, mask the eyes of the sensor that are receiving the direct light, using
electrical tape. (Caution: this disables the sensor operation in that direction).
4. Mount sensors so that light fixture is not below the sensors.
To avoid problems with EMI noise:
1. Do not mount IR sensors near suspect fixtures.
2. Do not run sensor connection cables near suspect fixtures.
3.3.3 RF Sensor Location Planning
Planning the location of RF sensors depends upon the facility. In most cases, for complete
coverage, they can be placed approximately 100 feet apart, because they have a sensitivity range
radius of approximately 50 feet. However, because concrete and steel structures absorb the RF
signal, and other materials affect the strength of RF signals, testing is necessary to determine the
best placement of RF sensors. When possible, avoid placing RF sensors in areas with an
overabundance of electrical devices, such as in a room with many computers.