pp2164 module 3 analogue addressable principles issue 3

PP2164/2009/Issue 3

Module 3

Analogue AddressablePrinciples

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Website: www.apollo-fi re.co.ukEmail: techsales@apollo-fi re.co.uk

Training Module 3PP2164/2009/Issue 3

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© Apollo Fire Detectors Limited 2004-2009

ContentsAnalogue Addressable Principles 3

Analogue Values from Detectors and A-D Converters 4

Control Panel Thresholds 5

Typical Control Panel Thresholds 5

Drift Compensation and Variable Sensitivity 6

Variable Sensitivity 6

Drift Compensation 6

Basic Communications: Voltage Pulse Polling 8

Current Pulse Response 9

Analogue Addressable Products 10

XPERT Card Addressing 10

DIL-Switch Addressing 11

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MODULE 3

Analogue Addressable PrinciplesAnalogue addressable fi re alarm systems are becoming increasingly sophisticated and have considerable advantages over conventional systems. They have the ability to pinpoint the exact location of fault and fi re conditions and can provide an extensive range of input and output functions.

In the case of ‘centrally intelligent’ systems, eg XP95, the control panel makes all of the decisions in terms of alarm conditions. The panel can confi rm the alarm condition by repeatedly interrogating the detector that is reporting the alarm ‘level’. The detectors simply report a value that is directly related to the amount of smoke (or heat) which is present.

ISO

ISO

ISO ISO ISO

ISO

ISOISO

Up to 20 devices

Output

Input

SCU

24V

240V

ZONEMONITOR

FIRE CONTROL

PANEL

I/O

SCU

I/O

Analogue

Addressable

Detector

Short Circuit

Isolator

SounderManual Call Point

Input/Output Unit

Sounder Control Unit

Remote

Detector LEDISO

© Apollo Fire Detectors Limited 2001/JDR

FIRECONTROL

PANEL

Figure 1: Typical loop confi guration


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Analogue Values from Detectors and A-D ConvertersXP95 smoke and heat detectors continuously monitor their environment and report an analogue value directly related to the amount of smoke (or heat) present.

In the case of the standard XP95 temperature detector, it is a very straightforward relationship between the analogue value and the temperature where the detector reports an analogue value of 25 at 25°C and 55 at 55°C.

In the case of the XP95 ionisation detector, as the sensing electrode voltage becomes more positive the analogue value increases proportionally (see Module 1 ‘Detection Principles & Device Selection’ for operating principles).

In the case of the XP95 optical detector, as the amount of light falling on the photodiode increases the analogue value increases proportionally (see Module 1 ‘Detection Principles & Device Selection’ for operating principles).

As the response from the detectors is analogue and the communication between the control panel and the devices is digital, it is necessary for each detector to carry out analogue to digital (A – D) conversions on a free-running basis. The latest A – D converted value is reported to the panel when that particular device is being ‘polled’ (interrogated).

Figure 2: Analogue to Digital (A – D) Conversion

0 X555545452525

Y Y-axisIonisation: voltage increaseOptical: obscuration % /mTemperature: increase

X-axis = digital count from analogue detector

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Control Panel ThresholdsIn an analogue addressable system, the fi re alarm panel uses set thresholds to determine the status of any given device on the loop. These thresholds are compared against the analogue values generated by smoke and heat detectors. XP95 detectors are designed to generate an analogue value of 55 at the same sensitivity as their conventional equivalent (Series 65) would latch into alarm condition (0.7Y value for ionisation and 3% obscuration for optical detectors).

The normal level for XP95 smoke detectors is 25 +/- 7. So any detectors reporting levels from 18-32 are considered ok. Any level outside these will require attention.

Typical Control Panel ThresholdsThe ‘pre-alarm’ level is designed to give an early warning that a detector is approaching a fi re condition. A pre-alarm is a condition that should be investigated but should not initiate a full alarm condition. It often gives the system user an opportunity to resolve a situation before a full evacuation is initiated, perhaps if cigarette smoke is building up or welding is taking place, the area can be ventilated before an alarm condition results.

The ‘fault’ threshold is designed to indicate that the sensitivity of a detector has dropped below an acceptable level. It is also used by some of the interfaces to indicate when there is a fault condition from a monitored device such as a remote detection device or power supply (interfaces generate an analogue value of 4 when reporting a fault condition).

Interfaces, call points and sounders have pre-set analogue levels. In normal conditions they report a value of 16. In fault they report levels of 4. The call points, switch monitors and zone monitors can report levels of 64 for a fi re condition.

Figure 3: Control Panel Response: Typical Thresholds

FaultFault

NormalNormal

Pre-alarmPre-alarm

FireFire

Digital Digital countcount

5555

4545

80


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Drift Compensation and Variable SensitivityDrift compensation and variable sensitivity are features of an analogue addressable system that can be accommodated either in the detector or in the control panel.

In the case of the XP95 devices, this feature may be incorporated into the control panel.

Variable SensitivityIn a basic XP95 system, the alarm threshold is always set to 55 counts which corresponds to the equivalent conventional Series 65 alarm threshold. If however, increased sensitivity is desired, this may be achieved by reducing the alarm threshold. The monitor is usually looking for a Delta change of 30 counts to generate an alarm condition (25 to 55). If the alarm threshold is reduced to 50, this results in a reduced Delta change being required to generate an alarm condition (25 instead of 30) thus increasing sensitivity.

Decreasing the sensitivity is achieved by simply increasing the alarm threshold. For example if the alarm threshold is raised to 65, this increases the Delta change to 40.

It should be noted that this method of variable sensitivity is only possible because the XP95 monitors have a truly linear response.

Drift CompensationDrift compensation is a signal processing algorithm that compensates for detector contamination or environmental conditions and maintains the desired sensitivity level.

Figure 3 shows the effect on the Delta change if the monitor analogue value increases as a result of a build-up of contamination:

Figure 4: Drift of clean air value

FaultFault

NormalNormal

Pre-alarmPre-alarm

FireFire


5555

4545

80

count = 30count = 30 count = 25count = 25Cleeann aaiirr vaaluue

count = 12count = 12

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Drift compensation is achieved by altering the alarm threshold in relation to the analogue value being reported such that a Delta change of 30 counts is maintained. See Figure 4 below:

The compensation should be carried out at an optimum rate such that the system will not fail to detect a slowly developing fi re.

If for example, the alarm threshold was increased by one count on every occasion that a reported value from a monitor increased by one count then a fi re condition would never be detected!

The drift compensation algorithm recommended by Apollo works in the following way:

1. The analogue value is sampled fi ve times every 640 seconds (a sample every 128 seconds)

2. If the average of the fi ve values is greater than the previously compensated analogue value, then the alarm threshold is increased by one count (regardless of how much greater the average value is).

3. If the average value of the fi ve samples is less than the previously compensated analogue value then the alarm threshold is reduced by one count (regardless of how much less the average value is).

The rate of compensation is such that the system is still capable of detecting the most slowly developing of fi res but is fast enough to compensate for cyclic variations over a 24-hour period.

Figure 5: Drift Compensation by Control Panel

Normal


5555

4545

80

count = 30Clean air value

count = 30

TimeTime

Pre-alarmPre-alarm

Fire

Fault

count = 30


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Basic Communications: Voltage Pulse PollingThis is how the control panel communicates with the devices on the loop. We have 17−28V DC to power the devices with 5−9V pulses imposed on top for polling (talking to) the devices on the loop. The spaces between these pulses are set to specifi c timings but basically a short duration between pulses is a ‘0’ and a long duration is a ‘1’.

The panel will poll each device and may ask devices to perform certain commands. Therefore the message sent out by the panel includes the selected device address and three forward command bits (output bits). The output bits may, for example, switch on the device LED, energise a relay or activate a sounder.

5-9V

17-28V DC

0 1 0

Figure 6: Voltage pulse polling

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Current Pulse ResponseAfter the control panel has sent out the initial voltage pulses used to poll a device, it then sends out a further series of regulated voltage pulses. These pulses are designed so that the selected device’s current pulses can be placed between them for a message that the control panel can interpret.

The device current pulse responses are 20mA in size (10mA for an IS device). The fi rst current pulse returned is the ‘interrupt’ bit. This is used by manual call points to signify an immediate response is required. Other information in the response could include the analogue value of the selected device, a confi rmation of a command, the type code of the device and an address confi rmation.

5-9V

17-28V DC

0 120mA

Figure 7: Current pulse response

2 10 6 5 4 3 2 1 06 5 4 3 2 1 0 2 1 0 2 1 0 6 5 4 3 2 1 0 4 3 3 2 1 0 6 5 4 3 2 1 0

Discovery protocol, read modeCurrent pulse response

Extended Bits not used

Discovery protocol – normal mode Alarm Parity

Panel to device flag Sensitivity bit Interrupt/Analogue value Input Device Address XP Extra data Drift alarm address

Output Address bits type confirmation flag type flagbits polled Interrupt bits

Figure 8: Discovery Protocol


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Figure 9: XPERT Card

2 8 32

1641 64

Analogue Addressable ProductsThe XP95 system is said to be a ‘centrally intelligent’ type system because the control panel makes all the decisions. Also, features such as sensitivity change and drift compensation are panel based.

Apollo also manufacture the Discovery range which offers greater fl exibility as it can be adapted to changing conditions and reduce unwanted alarms. A Discovery system is said to have ‘distributed intelligence’. Each detector in the Discovery range can operate in one of fi ve response modes that can be selected from the control panel. Mode selection depends on application: mode 1 will give a higher sensitivity to smoke than mode 5. This means that a detector set to mode 1 will be suitable for cleanrooms while one set at mode 3 will be better suited to an offi ce environment and one set to mode 5 could be used in a loading bay. Drift compensation is also incorporated into the detector head, adapting to dirty or dusty environments, which reduces the number of false alarms. Please see Module 3.2 and Appendix A for more details.

XPlorer is Apollo’s basic or entry-level analogue system. It is useful for designers who are familiar with our conventional ranges but want the benefi ts of using an analogue system without the complex design and commissioning. This range is for small to medium sized installations. Please see Module 3.3 for more information.

XPERT Card AddressingAnalogue addressable detectors are addressed using the unique, patented XPERT card which provides simple, user friendly and accurate identifi cation of detector location. A coded card is inserted into the base and is read by any detector head once it is plugged in. All the electronic components are in the detector but the location information is held within the base. The advantage of this type of addressing is that the address is maintained in the base not in the detector, therefore the location information always remains relevant.

The XP95 system allows up to 126 addressable devices to be connected on a single pair of wires (usually in a loop). Each device in the circuit has its own unique binary coded address. This is a 7-bit address which is set on an XPERT card (monitors) or a DIL-Switch (interfaces and manual call points). The 7 bits actually allow 128 binary combinations, however, 0000000 and 1111111 are invalid for normal addressing.

The XPERT card, which is inserted into the XP95 base, has seven removable pips that are used for address setting. These pips are designed to compress switches on the rear of the monitor thus making the address. The address bits correspond to the pips that are removed from the XPERT card not the ones which remain.

The binary weighting of each pip is identifi ed on the XPERT card.

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Figure 10: DIL-Switch

© Apollo Fire Detectors Limited 2006-7/DJO/TP

1 2 3 4 5 6 7ON

0 1 0 11 1 0

Address 78 =

Example:

ON = 0

DIL-Switch AddressingManual call points and Interfaces are addressed using a 7-bit DIL-Switch. The switches are marked 1 to 7, 1 being the least signifi cant bit and 7 being the most signifi cant bit. The DIL-Switch uses reverse logic (‘ON’ is 0 and ‘OFF’ is 1).


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Differences between XP95 and Discovery

XP95 detectors report back a value to the control panel, known as the analogue value, dependent upon how much smoke or heat is present in the area they are sited, the more smoke or heat the higher the value. The control panel would then make the decision to sound the alarms etc once the detectors analogue value had reached a preset threshold. The reported analogue value of 55 is equal to the alarm sensitivity of the detector set out in En54 part 5 for heats and part 7 for smokes. The control panel could also allow for the thresholds to be changed so that a detector could become more or less sensitive. Software could also be produced for Drift Compensation algorithms within the panel.

The type of system the XP95 detectors are connected to would have ‘Centralised Intelligence’.

Discovery detectors have most of the processing described above within the detector (so the type of system it would be connected to would have ‘distributed intelligence’) including: -

5 levels of sensitivity and different times to alarm (or Integrating periods which may reduce false alarms)

Different modes numbered 1 – 5 where 1 = Most Sensitive and 5 = Least Sensitive

Day/Night Modes – Sensitivity can be switched automatically via the control panel.

So, for example: -

In a factory – Low (Mode 5) during normal working hours or High (Mode 1) outside these times.

In a restaurant/club – High during the day when empty or Low at night when full

Or the Multisensor is very fl exible for use in areas requiring switchable modes, especially with its ‘Heat only’ mode. An example of this might be in a Theatre or Function Room where a switch from smoke to ‘Heat only’ might be required when these areas are being used.

Also a Multisensor in Mode 4 (combination smoke and heat in low sensitivity) has been useful in hotel / student accommodation where a resistance to steam/cooking fumes is required.

Multi in Mode 1 = V Sensitive Combination Smoke and Heat.Multi in Mode 2 = Normal Smoke only.Multi in Mode 3 = Mid Range Combination Smoke and Heat. (XP95 Multisensor setting)Multi in Mode 4 = Lower Sensitivity Combination Smoke and Heat.Multi in Mode 5 = Grade 1 (A1R) Heat detector.

Discovery Heat Detectors

Essentially 5 Heat detectors in one unit, so there is no requirement to change the detector because of a problematic area (i.e. the detector is near an oven in an industrial kitchen), simply change the mode.

Drift Compensation For Smokes

So that the build up of dust or dirt around the sensing elements of a smoke detector does not effect the sensitivity of the device. When the detector cannot compensate further it sends a signal to the control panel (called the drift fl ag) and the panel gives a ‘fault’ alert. The detector then needs to be cleaned.

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Read / Write To Detector Memory

Useful for storing Apollo based data i.e. date of manufacture, approvals info.

4 bytes put aside for customer use, applications include date of commission, date of last service, user code.

LEDs

Dual LEDs for all round visibility. Flashing LED (Global or single point) option.

Also

ALL detector modes are approved to EN54 parts 5 for heats and 7 for smokes. (Not all competitors can say the same)

They use the same bases as XP95 with our patented XPERT card. They use virtually identical protocol and can be used on XP95 and S90 systems. They can be used with XP95 Interfaces and sounders.

WM130303

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Please answer the following questions:

1. How many addresses are available on an XP95 loop?

2. What analogue value would an XP95 temperature monitor report if the room temperature was 30°C?

3. At what analogue value would a pre-alarm be initiated?

4. When the analogue value equals 55, how much smoke is in an XP95 optical chamber?

5. What Delta change in counts is normally required to generate an alarm?

6. Give an example of what an output command bit might achieve.

7. What size is the current pulse from an IS device?

8. How many 'modes' do Discovery detectors have?

9. In Discovery, which mode is most sensitive?

10. To set the address, what should be done with the pips in the XPERT card?

Module 3: Analogue AddressablePrinciples Test

pp2164 module 3 analogue addressable principles issue 3

Documents

voltage pulse polling

manual call points

previously compensated analogue

current pulse response

patented xpert card

control panel makes

analogue addressable system

call points