1. Insufficient coverage. This can be caused by either installating sensors to far apart, i.e installing 5m diamter sensors on a pitch greater than 5 metres will cause 'dead spots' or installaing a sensor that exagerates its performance.
2. Obstructions. Positioning of Sensors mustt be sympethetic to the furniture layout. For example, position a tall filing cabinet between the sensor and person then coverage will be impaired.
The other cause of this are poorly designed Presence Detectors. A Presence Detector is made out of two main parts. Firstly, there is the Passive Infra-Red detector. This is a device that detects a combination of movement and heat and looks like a transistor with three legs and clear top for detection. This is then physically joined electronicly to an electronic amplifier. This amplifier amplifys the very low voltage from the P.I.R (measured in micro volts) to a usable voltage for a microprocessor (3 volts plus). The connection between the P.I.R and the amplifier is normally by copper track on a circuit board. these copper tracks behave like aerials. It is not unusual for voltages high enough to be in the environment from other sources that the amplifier will boost into a signal to the microprocessor and cause false triggering. To avoid this it is normal for the sensor to be 'de-sensed' to provide stability but at the expense of performance.
The Steinel range of Presence Detectors contain a quad sensor for geniune 360 degree viewing and an internal amplifier within the P.I.R metal housing eliminating the 'ariel' that in turn enables us to produce a Presence Detector without compromise on performance. As a bonus, it is available both as a surface as well as a flush mount making it inconspicuous.
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