Description

The heat sensing is provided by a thermistor. The temperature at which the device goes into fire is defined by the configuration settings in the control panel. The control panel also calculates any rate of rise elements required in the fire decision. The optical sensing is performed by the dual angle optical chamber, which has two transmitting LED1 and LED2, plus an infrared receiver. Normally measurements are taken at regular intervals at both angles of the chamber. The panel uses both readings to form a ratio. The ratio is used to compensate the optical sensor, producing a very flat response to different fire types. There are distinct bands of ratios that define the presence of types of smoke, dust or steam. The dual optical sensor is therefore able to discriminate between certain aerosol in the environment. Additionally to stop the sensor saturating with large false alarm signals the sensor incorporates an extended dynamic range. The sensor is therefore suitable for use in wider applications where steam and dust particles may occasionally be present.