Classifications

• • G—PHYSICS
  • G08—SIGNALLING
  • G08B—SIGNALLING SYSTEMS, e.g. PERSONAL CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
  • G08B29/00—Checking or monitoring of signalling or alarm systems; Prevention or correction of operating errors, e.g. preventing unauthorised operation
  • G08B29/12—Checking intermittently signalling or alarm systems
  • G08B29/123—Checking intermittently signalling or alarm systems of line circuits
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04B—TRANSMISSION
  • H04B3/00—Line transmission systems
  • H04B3/02—Details
  • H04B3/46—Monitoring; Testing
• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
  • G05B19/00—Program-control systems
  • G05B19/02—Program-control systems electric
  • G05B19/04—Program control other than numerical control, i.e. in sequence controllers or logic controllers
  • G05B19/042—Program control other than numerical control, i.e. in sequence controllers or logic controllers using digital processors
• • G—PHYSICS
  • G05—CONTROLLING; REGULATING
  • G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
  • G05B23/00—Testing or monitoring of control systems or parts thereof
  • G05B23/02—Electric testing or monitoring
  • G05B23/0205—Electric testing or monitoring by means of a monitoring system capable of detecting and responding to faults
  • G05B23/0218—Electric testing or monitoring by means of a monitoring system capable of detecting and responding to faults characterised by the fault detection method dealing with either existing or incipient faults
  • G05B23/0256—Electric testing or monitoring by means of a monitoring system capable of detecting and responding to faults characterised by the fault detection method dealing with either existing or incipient faults injecting test signals and analyzing monitored process response, e.g. injecting the test signal while interrupting the normal operation of the monitored system; superimposing the test signal onto a control signal during normal operation of the monitored system

Definitions

• the present invention relates to the installation and commissioning of fire alarm systems on a premises.
• Fire alarm systems are installed in many premises, such as office buildings, factories, homes, and the like, and typically include a fire alarm control panel (often known as control and indicating equipment, CIE), a number of detectors and sounders, and wiring connecting the detectors and sounders to the fire alarm control panel.
• CIE control and indicating equipment
• the system might also include call points and a range of other ancillary modules.
• the wiring which is installed is a 2 wire addressable loop, and the detectors, sounders, call points and other ancillary modules (hereafter called "the devices") are arranged on the loop connected across its 2 wires. Multiple loops are generally installed from the control panel, with each loop typically carrying the devices to a different part of the premises.
• the loops typically provide power to the devices on the loop, and convey instructions and data from the control panel to the individual devices, such as configuration data to all devices or an alarm signal to the sounders, and convey data from the devices to the control panel, such as an indication that a fire has been detected.
• the looped arrangement means that there is some resilience to a break in an individual loop occurring during operation and that the voltage level between the wires in the loop are maintained sufficiently high to sustain all of the devices around the complete loop.
• a fire alarm control panel can support up to 16 loops, and each loop can support up to 250 devices.
• communication on the loop uses frequency shift keying (FSK)) with sinusoidal signals on a DC pedestal of 37.6V.
• FSK frequency shift keying
• Each loop can be as long as 2000 m, and the cable used to form it might be supplied by different manufacturers, so they have different resistance, capacitance and inductance. Resistance affects the DC voltage level. Capacitance can cause signals to be attenuated as they pass through it. If attenuation is too high, it can negatively affect communication between the control panel and the devices, potentially resulting in false alarms being triggered, or even no alarm being signalled when a fire condition is present.
• a portable commissioning tool is often used which is connected to the ends of the wires that will form a loop.
• the portable commissioning tool such as the MX TrueStart tool, tests the loop by ensuring that each wire has continuity, and by applying a DC voltage across one end of the loop and testing that the voltage at the opposite end of the loop is maintained at a sufficiently high voltage that it is able to operate all of the devices around the loop.
• the portable commissioning tool also communicates with each device on the loop once they have been installed in order to configure them, as appropriate.
• An aim of the present invention is to improve the testing of the system during commissioning in order to reduce faults which arise later and to measure the quality of signal communication through the cabling so that the quality of cables used is sufficiently high, even if the cables used are sourced from different manufacturers and are made to different specifications.
• a method of determining the quality of signal communication of a two-wire addressable fire alarm loop comprises: generating a string of test bytes; applying the string of test bytes across one end of the loop; receiving the string of test bytes across the other end of the loop after passing through the loop; comparing the received string of test bytes with the generated string of test bytes; and determining the quality of the signal communication of the loop based on the number of test bytes in the received string of test bytes which do not match the test bytes in the generated string of test bytes.
• the present invention is intended to reduce the number of faults which are found later in the commissioning process and after commissioning of a fire alarm system is complete by determining the quality of signal communication of a two-wire addressable fire alarm loop, especially where the cables used to form the two-wire cabling might be supplied by different manufacturers so they have different electrical properties. This can cause signals to be attenuated as they pass through it. If attenuation is too high, it can negatively affect communication between the control panel and the devices, potentially resulting in false alarms being triggered, or even no alarm being signalled when a fire condition is present.
• a method of determining the quality of signal communication of a two-wire addressable fire alarm loop comprises: generating a string of test bits; applying the string of test bits across one end of the loop; receiving the string of test bits across the other end of the loop after passing through the loop; measuring the pulse width of the test bits in the received string of test bits; and determining a measure of the quality of the signal communication of the loop based on the number of test bits in the received string of test bits which have a pulse width greater than a pulse width error threshold.
• a fire alarm loop tester arranged to test the quality of signal communication of a two-wire addressable fire alarm loop
• the tester comprises: a signal generator (11) arranged to generate a loop signal encoded with a string of test bytes; a signal terminal (3) arranged for connection across one end of a loop being tested and arranged to apply the loop signal across that end of the loop (2); a receiver circuit (15) arranged for connection across the other end of the loop and arranged to receive the loop signal across that other end of the loop after passing through the loop, and arranged to decode the received loop signal to give a received string of test bytes; and a processor for outputting the quality of the signal communication of the loop based on the number of test bytes in the received string of test bytes which do not match the test bytes in the generated string of test bytes.
• Figure 1 is a schematic diagram of a fire alarm system and a portable commissioning tool which forms part of the present application;
• FIG. 2 is a schematic diagram of a fire alarm system and a portable commissioning tool according to the present invention with a part of the commissioning tool being shown in more detail with a receiver circuit;
• Figure 3 is a diagram showing a test byte of a loop signal applied to one end of a loop 5;
• Figure 4 is a flow diagram showing a method of determining the quality of signal communication of a two-wire addressable fire alarm loop according to the present invention.
• FIG. 1 shows a fire alarm system 1 having 2-wire addressable network wiring in the arrangement of a loop 2 with two ends, a number of addressable networked devices 4 attached to the addressable network loop 2, and a portable commissioning tool 5 having four terminals 3 to which the ends of the loop 2 are connected.
• the addressable networked devices 4 can be any of a range of different fire alarm system devices, including : sensors 4a such as smoke detectors, heat detectors, fire detectors and the like; notification devices 4b such as sounders and strobes; and other ancillary modules such as call points 4c which are typically found on the loop of a fire alarm system.
• the devices 4 are connected across the wires of the loop such that they are powered from the loop and are able to transmit and receive data to and from other devices on the loop, such as the portable commissioning tool 5.
• Base units are often connected directly to the wires of the loop, and the devices may then be attached to the base units for easy connection to the network loop at a location defined by the position of the base unit (not shown).
• the portable commissioning tool 5 is able to test an addressable network loop 2 and the devices 4 which are positioned on the loop 2. If it detects a fault with the loop 2 or any of the devices 4, the wiring commissioning tool will identify it and indicate the fault in its display 6.
• the devices can be configured by an installation technician using a user input 7 on the portable commissioning tool 5 in the form of buttons.
• Figure 2 shows the fire alarm system of Figure 1 in which a part of the portable commissioning tool 5 is shown in more detail with its electronic components arranged in a block diagram.
• the tool 5 is connected to the loop 2 with the networked devices 4 located on the loop 2.
• the loop is a two wire loop having a first wire 21 and a second wire 22, and the loop has a left end 27, 28 and a right end 29, 30 each connected to a terminal 3 of the portable commissioning tool 5.
• the portable commissioning tool 5 includes a signal generator 11 which, during a test, generates a loop signal encoded with a string of test bytes, and that string of test bytes is supplied to one of the terminals 3 which applies the loop signal to the left end 27, 28 of the loop.
• the encoding used to modulate the loop signal is frequency shift keying (FSK) using sinusoidal signals on a DC pedestal of 37.6V.
• FSK frequency shift keying
• FIG. 3 The general structure of a data packet under this encoding method is shown in Figure 3 in which the packet comprises: a header; a byte comprising an 8 bit data packet; and a stop bit. The data is encoded such that the frequency of a "0" is much higher than the frequency of a "1".
• the opposite, right, end of the loop 29, 30 is connected to the other of the terminals 3 so that the right end of the loop 2 is connected to a receiver circuit 15. This enables the received loop signal to be received and decoded.
• the receiver circuit 15 comprises a first stage, which is a capacitive attenuator circuit 16, followed by a second stage which decodes the bytes and the bits of the received loop signal.
• the second stage involves parallel circuits : a decoder circuit 17 and an overcurrent detector circuit 18.
• the attenuator circuit 16 couples the FSK signal to the decoder circuit 17.
• the decoder circuit receives the attenuated received loop signal in this embodiment.
• the decoder 17 generates a decoded byte signal in the form of a PWM signal.
• the portable commissioning tool 5 includes a micro-controller unit (MCU) which includes a 16-bit analog to digital converter (ADC) and a processor, neither of which are shown independently in Figure 2.
• the micro-controller is a Renesas R5F565NEDDFP.
• the decoded byte signal and the decoded bit signal are directed to the processor which determines the quality of the signal Byte comparison and bit comparison is done by the processor.
• the extent to which the test bytes of the decoded loop signal (the decoded byte signal) match the test bytes applied to the loop depends on the transmission quality of the loop itself. The worse the transmission quality, the greater the number of mismatches.
• the system is able to operate within a transmission quality range, but once the number of mismatches exceeds a certain level, the quality of the transmission through the loop is at a level where the system may not function properly.
• By measuring the number of mismatches it is possible to assess whether the transmission quality of the loop is lower than a threshold for reliable data transmission through the loop. This might be done, for example, by comparing the number of mismatches between the test bytes of the decoded loop signal and the test bytes of the loop signal applied to the loop.
• the extent to which the test bytes of the decoded loop signal match the test bytes applied to the loop depends on the transmission quality of the loop itself. The worse the transmission quality, the greater the number of mismatches.
• the extent to which the test bits of the decoded loop signal (derived from the decoded byte signal) match the test bits applied to the loop also depends on the transmission quality of the loop itself. The worse the transmission quality, the greater the number of mismatches.
• the system is able to operate within a transmission quality range, but once the number of mismatches exceeds a certain level, the quality of the transmission through the loop is at a level where the system may not function properly.
• By measuring the number of mismatches it is possible to assess whether the transmission quality of the loop is lower than a threshold for reliable data transmission through the loop. This might be done, for example, by comparing the number of mismatches between the test bits of the decoded loop signal and the test bits of the loop signal applied to the loop.
• the extent to which the test bits of the decoded loop signal match the test bits applied to the loop depends on the transmission quality of the loop itself. The worse the transmission quality, the greater the number of mismatches.
• switch controller 13 If there is a switch array 12, it is configured using the switch controller 13 such that the signal generator 11 is connected to the terminal 3 to which the left end 27, 28 of the loop is connected, and the receiver circuit 15 is connected to the terminal 3 which is connected to the right end 29, 30 of the loop.
• the switch controller 13 might be controlled by a main MCU.
• step 75 the signal generator 11 is activated to generate the loop signal encoded with the string of test bytes described above using FSK encoding.
• Each test byte includes 8 test bits, and 8 bytes are generated as dummy command data in a pulse lasting for 25ms.
• the dummy command data in this example is: (0x01, 0x78, 0x99, 0x12, 0x34, 0x82, 0x27, 0xE5).
• the pulse is paused for 15 ms to allow for the loop signal to be processed in steps 77 to 83 below, and the pulse is repeated. In this example, the pulse of dummy command data is sent 100 times.
• step 77 the loop signal is applied to the left end 27, 28 of the loop so that it propagates along the length of the loop.
• the loop signal reaches the right end 29, 30 of the loop, it is received in step 79 by the terminal 3 to which the right end 29, 30 of the loop is connected.
• step 81 since the receiver circuit 15 is connected to the terminal 3, the received loop signal is received by the receiver circuit 15 and is attenuated by the attenuator circuit 16.
• step 83 the attenuated received loop signal is passed to the decoder circuit 17 and to the overcurrent detector circuit 18.
• the decoder circuit decodes the received loop signal to produce a decoded byte signal.
• the byte signal is directed to the micro-controller unit (MCU).
• MCU micro-controller unit
• Step 85 involves comparing the decoded string of test bytes with the string of test bytes applied to the loop using the processor of the micro-controller MCU. It identifies which of the bytes match, and which do not, and generates a byte error signal.
• a decoded string of test bits is analyzed by the processor of the micro-controller MCU by measuring the pulse width of every bit. If the width of a bit is between 7 and 23 FW counts of a timer, corresponding to about 37 to 123 microseconds, the bit is determined to be a "1". If the width of a bit is between 24 and 40 counts of the timer corresponding to about 128 to 213 microseconds, it is determined to be a "0". If the width of the bit is more than a pulse width error threshold of 40 counts of the timer, a bit width error is determined to have occurred.
• each of the pulses of dummy command data is processed through steps 75 to 85 in turn, which allows time for all of these steps to be completed.
• step 87 the processor of the micro-controller MCU determines the signal quality from the number of byte errors and from the number of bit width errors. The more byte errors and bit errors, the lower the quality of signal communication of the loop. If the number of byte errors and/or bit errors is below a lower threshold, the quality of signal communication of the loop is rated as 'excellent'. If the number of byte errors and/or bit width errors is above the lower threshold but below an upper threshold, the quality of signal communication of the loop is rated as 'good'. If the number of byte errors and/or bit width errors is above the upper threshold, the quality of signal communication of the loop is rated as 'poor'. In this embodiment, the lower byte threshold is 100 and the upper byte error threshold is 1000, the lower bit width error threshold is 1000, and the upper bit threshold is 5000. This gives ranges for the ratings:
• the worst of the two ratings is used. However, in other embodiments, it might be appropriate to use the better of the two ratings, or to combine the different results in some way, perhaps also with some other measure of the signal quality to determine the rating.
• the quality might be determined by the proportion of the test bytes or bits which are byte errors or bit width errors. It will be appreciated that using only one of the byte errors or bit width errors might be enough to rate the signal quality, but it is advantageous to use both because it gives more data comparison points for a particular loop signal, either improving accuracy of the assessment of the signal quality, or permitting the signal quality to be assessed more quickly using a shorter loop signal than if only one type of error were used.

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• Engineering & Computer Science (AREA)
• Computer Security & Cryptography (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Computer Networks & Wireless Communication (AREA)
• Signal Processing (AREA)
• Selective Calling Equipment (AREA)
• Fire Alarms (AREA)

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• 2023
  • 2023-08-31 GB GB2313306.9A patent/GB2633079A/en active Pending
• 2024
  • 2024-08-29 EP EP24765363.7A patent/EP4771607A1/de active Pending
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