SERIES 65 optical smoke detector

The SERIES 65 optical smoke detector is a conventional smoke detector composed of a self-extinguishing, white polycarbonate housing with wind resistant smoke inlets. Nickel plated stainless steel wiper contacts connect the detector to the base.

The SERIES 65 optical smoke detector works on the light scatter principle and is ideal for applications where slow burning or smouldering fires are likely.

• responds well to slow burning, smouldering fires
• well suited for bedrooms and escape routes
• unaffected by wind or atmospheric pressure

Inside the case a printed circuit board has the optical system mounted on one side and the signal processing electronics on the other. The sensing chamber is a black moulding configured as a labyrinth which prevents penetration of ambient light. The labyrinth has a fine gauze insect-resistant cover. The chamber houses an infrared light emitting diode (LED) and a photo-diode which has an integral visible-light filter as extra protection against ambient light.

Every three seconds the LED emits a burst of collimated light. In clear air, light from the LED does not fall directly on the diode because the LED is positioned at an obtuse angle to the diode. When smoke enters the chamber, a fraction of the collimated light is scattered onto the photo-diode. If the resulting signal from the photo-diode is above a pre-set threshold, the LED emits two more bursts of light, this time at two-second intervals. If light is scattered onto the photo-diode by both these pulses - due to the presence of smoke - the detector signals an alarm state.