scada saif
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Prerequisite
Bit is binary representation 0 or 1.
One byte contains 8 bits.
Baud rate is used to express totalcapacity of communication channel.
Bandwidth is the frequency range of
channel.
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Modulation
The process of superimposing lowfrequency signal on a high frequency
carrier is called modulation.
Demodulation
Extraction of base band signal fromhigh frequency carrier.
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Transmission
Synchronous & Asynchronous
Synchronous transmission
The transmission is started with startbit and continuous the transmissionends with a stop bit.
Asynchronous transmission deals inform of frame including start andstop bit total 10 bits.
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Communication Channel
Half Duplex
Full Duplex
Half duplex channel can send andreceive but not at the same time.
Full duplex channel can send andreceive at the same time.
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Switching techniques
Circuit Switching
Dedicated communications pathestablished for the duration of theconversation
e.g. telephone network
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Packet Switching
Data sent out of sequence
Small chunks (packets) of data at a
time Packets passed from node to node
between source and destination
Used for terminal to computer andcomputer to computercommunications.
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SCADA
Supervisory Control And DataAcquisition.
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Communication Media
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Satellite Communication
Equipment
RFT
Modem
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Remote Terminal Unit
Communication with control centre.
Acquisition of status signal.
Sequential event recording. Remote diagnostic facilities.
Connection of subordinate terminals.
Print out of events. Review
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Collector 400
Remote Terminal Unit.
Local data acquisition and dataprocessing.
Reporting and control.
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Control Commands
Two types of commands
Item Control commands are normallycarried out using two step procedure.
Examples are circuit breaker anddisconnectors.
Regulation command are carried out
single step procedure. Example ofregulated equipment and tapchangers on transformers.
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Function in collector 400
It uses local input output systemwith analog input board, digital
output boards, energy pulsecounter, command board, digitaland analog output boards.
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Standard Additional Functions.
Permanent Connection.
Reconnectible.
Radio link equipment. Local alarm with communication
failure.
Both half and full duplexcommunication.
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Modular system assembly
Contains back plane for 19 racks.
Plug in units for 19 racks.
Base boards, processor boards andexpansion boards.
Extension boards.
Connection units.
P I t f S t
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Process Interface System
The DS100l0 system includes units forinterfacing between computer and theprocess i.e.
Digital input and output boards.
Analog input and output boards.
The signals are converted in interface
board for transmission as A/D, D/Aconversion. Filtering, rectificationamplification.
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Single board computer
It is provided with V24 channels forconsole communication.
DSPC 155 is designed around 32 bitinternal structure 4 MB of internalmemory and 4 MB virtual memory. Eprom of 320 KB. Internal memory of
512 KB.
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Memory board DSMB 110
The board contains high capacity 128KB dynamic read / write memory.
The board functions as asynchronousstatic memory.
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Communication board with line
selector DSCA 140
Three communication ports with V24.
Port is selected on board logic.
Synchronous communication can beused.
Programmable baud rate.
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What is multiplexing.
Different kind of data transmittedover single line.
Example is voice, data, fax, etc.
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Floppy disk unit DSMC 110
It can control two floppy units ofBASF 6108 type or similar with 5.2
Voltage required by floppy disk unitsare provided by the DSMC 110.Theunit is equipped with a 256 bytessector buffer for reading and writing.
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Pulse counter Board
Board is galvanically isolated by otherparts by mean of opt couplers.
There are other digital and analoginput output boards with differentspecifications.
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CTU
Collector test unit is a test unit forRTU.
CTU is software loaded in PersonalComputer.
Almost all controlling is made with 8dynamic function keys(F1-F8).
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Multiplexer
30 user channels of 64K bandwidthcan
be combined into an E-1 circuit.
E1- Mux
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Cards used in mux
V.35 is used for data.
LGS is used for voice.
Dsp is application card for voicecompression.
E1 is basic channel communication
card.
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Where Mux is needed ?
Mux is not generally used in applicationswhere a client simply has a leased line andwants to send only data traffic. In this
case they would simply use two DTUs(Data Termination Unit) at their twopremises to extend the digital connection.
Also mux can be used when the wan
connectivity is not through leased line butradio modems or satellite modems.
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Modulation using FSK modem.
Values represented by different values.
Less susceptible to errors.
Up to 1200bps on voice grade lines.
High frequency radio. (3 to 30 MHZ)