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The LIFFE control room |
Managing the essential services of large commercial buildings can be daunting at the best of times.Firstly, the large number of systems to be monitored and controlled requires numerous channels of communication between input modules,output modules,and a central control unit.Inputs include switches,light and temperature sensors, control panels and smoke detectors,while output modules are typically relays that control equipment such as lighting,heating or air-conditioning units,fans,boilers,and pumps.Secondly,flexibility is a must,as unforeseen changes and modifications are a fairly common occurrence.Finally,disruptions to a building's operation must be kept to an absolute minimum,as they can incur heavy financial losses.
However,Dave Bruce,Director of Premises and Engineering at Euronext.liffe was facing an even tougher challenge.Situated in the City of London,the building is the home of Euronext.liffe,the international derivatives business of Euronext,comprising the Amsterdam,Brussels,Lisbon,LIFFE and Paris derivatives markets.
Euronext.liffe is the world's second largest derivatives exchange by value with over 1,000 billion Euros through its market every day.
The electronic trading platform LIFFE CONNECT provides access to this fully electronic exchange 24 hours a day,7 days a week,365 days a year,at over 790 sites worldwide.These locations are in 29 different countries,covering all major time zones.There is simply no room for downtime at Euronext.liffe – it is imperative to the markets that the building remains operational at all times.
Ideal for monitoring
Carlo Gavazzi's Dupline installation bus turned out to be ideal for monitoring the building's essential services.Its simple but effective time-division multiplexing scheme accommodates up to 128 signals on a single two-wire cable,massively reducing the amount of cabling required.An equivalent hard-wired system would have produced a confusing proliferation of cables and made maintenance more difficult.A total of eight Dupline networks are installed in the Euronext.liffe building in London to cover all essential services and alert the engineering team to any problems.Timing signals for each bus are produced by a G 3 4 9 0 0 0 0 0 8 2 4 Channel Generator,with individual data channels represented by consecutive pulses lasting one millisecond.
Essential equipment is fitted with G 3420 5501 800 eight-channel input modules,which transmit fault information to the control room by varying the duty cycle of the respective pulse.The fault signals indicate incidents such as a person stuck in a lift pressing the alarm button,air chillers for the air-conditioning system not operating,and a wide range of other possible malfunctions.Faults are monitored in the control room so that maintenance can be carried out quickly and discreetly without affecting the day's trading.
Besides its primary purpose in fault monitoring,the Dupline system also serves as a manual back-up control system in case of a failure of the main building management system.Essential equipment is controlled through G 3430 5511 800 eight-channel receivers with NPN open-collector outputs that can directly drive large relays.
A high degree of flexibility
The Dupline system's robust signalling scheme and low carrier frequency of 1kHz provide excellent noise immunity,enabling reliable transmission of digital and analogue signals over ordinary unshielded two-wire cables up to several kilometres long.There are no restrictions on bus topology,which can be linear,circular, starshaped or any combination of these.Dupline also provides a high degree of flexibility,as extra components can be added with a minimum of effort.New modules are simply assigned an unused bus address using the handheld GAP 1605 coding tool and connected to the bus at any location.The only additional cabling required is a pair of wires between the new module and the existing bus.Many input modules,such as switches and sensors,can draw their supply current directly from the Dupline bus,eliminating external power supplies and their associated risk of failure.All Dupline modules interoperate seamlessly,and although today's modules use modern ASIC technology,they are still compatible with modules installed 17 years ago.
A good discovery
Dave Bruce discovered Dupline about 12 years ago while searching for a solution for hard-wiring monitoring systems at LIFFE.He initially bought one set and wired it up on his desk.The system was easy to set up and did the job with a minimum of complexity,so Dave decided to use it.Whenever he buys any new equipment or plant now,Dave specifies that the Dupline system be installed into it by the manufacturer.
Dupline has proven its performance in over 100,000 installations worldwide,with applications ranging from building automation to water distribution, energy management and railway systems.
Solutions are engineered by combining products from a wide range of modules,including digital and analogue input/output modules,PLC and PC interfaces,touchscreen control units,modems and the Dupline Controller.All modules in an installation connect to the same two- ire bus.Since signals transmitted on the bus can be received by any other module programmed to listen on the same channel,Dupline systems can operate with or without a central control unit.In the latter case,input modules communicate peer-to-peer with output devices.Signals can be transmitted not only on copper wires,but also through fibreoptic cables,leased telephone lines,a radio modem.Yet another option is a GSM modem,which sends SMS messages to one or more mobile phones in case of a fault,and enables remote control via SMS commands.
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