Apollo Discovery Ionisation Smoke Detector (58000-500APO)

The Discovery Ionisation Smoke Detector uses a low activity radioactive foil to detect fires by irradiating the air in the smoke chambers and causing a current flow. If smoke enters the chamber, the current flow is reduced leading to an alarm.

Operation

The Discovery Ionisation Detector uses the same outer case as the optical smoke detector and is distinguished by the red indicator LEDs. Inside the case is a printed circuit board which has the ionisation chamber mounted on one side and the signal processing and communications electronics on the other. 

The ionisation chamber consists of a reference chamber contained inside a smoke chamber.The outer smoke chamber has inlet apertures fitted with insect resistant mesh. 

At the junction between reference and smoke chambers, the sensing electrode converts variations in chamber current into voltage changes.

When smoke particles enter the ionisation chamber, ions become attached to them with the result that the current flowing through the chamber decreases. This effect is greater in the smoke chamber than in the reference chamber, and the imbalance causes the sensing electrode to become more positive.

The analogue voltage at the sensor electrode is converted to a digital format which is processed to provide an analogue value for transmission to the fire control panel when the device is polled.

Communication

Discovery uses a digital communications protocol which has been developed from the XP95 protocol but differs in that it allows communication in three different modes: (Normal, Read and Write) to allow a more extensive exchange of information and commands than previous analogue addressable ranges. In addition, Discovery can store data in non-volatile memory. 

The Normal mode is identical to the XP95 protocol with the exception that the five additional analogue value bits in the XP95 protocol extension have been re-defined so that the fire control panel is able to distinguish between Discovery and XP95 devices.

The Read mode is used to check information stored in the non-volatile memory of each detector. It is accessed by using a simple extension to the Normal mode communication method from the fire control panel to the detector.

In Write mode the fire control panel is able to write information to the detector by extending the communication method in the same way as in Read mode. During Read or Write modes a detector can signal an alarm by means of the alarm flag and alarm address bits.

Discovery detectors are compatible with XP95 and Soteria. It should be noted, however, that Discovery features will not be available when Discovery is used with XP95 fire control panels. Fire control panels with drift compensation algorithms should disable the algorithms when communicating with Discovery.

For fire control panels running CoreProtocol, please refer to the fire control panel manufacturer’s operating instructions.

Environmental Characteristics

The Discovery Ionisation Detector, like all ionisation detectors, has some sensitivity to air movement (wind). The extent to which the analogue value will change depends on the wind speed and on the orientation of the detector relative to the wind direction. Relatively small changes in wind direction can cause significant changes in analogue value.

For wind speeds up to 1m/s the change in analogue value will not exceed 5 counts. Continuous operation in wind speeds greater than 2m/s is not recommended. However, wind speeds up to 10m/s can be tolerated for short periods and will not under any conditions increase the probability of false alarms.

Ionisation smoke detectors are supplied in individual packing with a red lid serving as a dust cover which can be left in place after fitting to prevent ingress of dust and dirt until commissioning of the system takes place. At this point the covers must be removed.

Mounting Bases are sold separately (click here to see compatible bases)

Watch the Video