There are two high performance fire sensors incorporated within the Rafiki Multipoint fire detector:
Optical scatter smoke sensor
Based on a high efficiency infra-red LED and receiver pair, the optical chamber includes two lenses and has been designed to be tolerant against the effects of ambient light, dust and insects, whilst giving a high signal/noise ratio for good electronic stability.
Heat sensor
Based on a selected thermistor heat sensor.
Research
Research into fire detection has shown that this is currently the best combination of sensors for giving a good response to a wide range of fires. The heat sensor can be used to boost the response of the optical sensor to free burning fires which produce a lot of heat. This negates the need for ionisation detectors which contain radioactive sources, and have an extremely poor response to smouldering fires. It also means that the specifier does not have to predict in advance the expected type of fire.
The signals from the sensors are processed with a microcomputer. Signals from the sensors are read every 400ms and a fire decision is taken every 5 seconds. This involves analysis using long term averaging as well as faster signals. A set of rules is processed which optimises the detection response depending on the detection mode selected, which gives the fastest response to fires whilst rejecting signals which could cause false alarms.
The background signal from the optical scatter smoke sensor is updated regularly to compensate for the effects of dust build up and long term ageing. Values are stored in non-volatile EEPROM memory, along with calibration data and the device serial number.
The Rafiki Twinflex Multipoint Detectors & Rafiki Twinflex Fire Alarm System are available now from Discount Fire Supplies.
This information has been referenced from an official Rafiki publication.
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