Automating Manufacturing Systems - Process Control and ...

plc glossary - 35.25
through capacitors that smooth it out. A small ripple still remains.
RISC (Reduced Instruction Set Computer) - the more standard computer chips were CISC (Complete
Instruction Set Computers) but these had architecture problems that limited speed. To overcome
this the total number of instructions were reduced, allowing RISC computers to execute faster,
but at the cost of larger programs.
rlogin - allows a text based connection to a remote computer system in UNIX.
robustness - the ability of a system to deal with and recover from unexpected input conditions.
ROM (Read Only Memory) - a permanent form of computer memory with contents that cannot be
overwritten. All computers contain some ROM to store the basic operating system - often called
the BIOS in personal computers.
rotameter - for measuring flow rate with a plug inside a tapered tube.
router - as network packets travel through a network, a router will direct them towards their destinations
using algorithms.
RPC (Remote Procedure Call) - a connection to a specific port on a remote computer will request that a
specific program be run. Typical examples are ping, mail, etc.
RS-232C - a serial communication standard for low speed voltage based signals, this is very common on
most computers. But, it has a low noise immunity that suggests other standards in harsh
environments.
RS-422 - a current loop based serial communication protocol that tends to perform well in noisy
environments.
RS-485 - uses two current loops for serial communications.
RTC (Real-Time Clock) - A clock that can be used to generate interrupts to keep a computer process or
operating system running at regular intervals.
RTD (Resistance Temperature Detector) - as temperature is changed the resistance of many materials will
also change. We can measure the resistance to determine the temperature.
RTS (Request To Send) - A data handshaking line that is used to indicate when a signal is ready for
transmission, and clearance is requested.
rung - one level of logic in a ladder logic program or ladder diagram.
R/W (Read/Write) - A digital line that is used to indicate if data on a bus is to be written to, or read from
memory.
35.19 S
safety margin - a factor of safety between calculated maximums and rated maximums.
SCADA (Supervisory Control And Data Acquisition) - computer remote monitoring and control of
processes.
scan-time - the time required for a PLC to perform one pass of the ladder logic.
schematic - an abstract drawing showing components in a design as simple figures. The figures drawn are
often the essential functional elements that must be considered in engineering calculations.
scintillation - when some materials are high by high energy particles visible light or electromagnetic
radiation is produced
SCR (Silicon Controlled Rectifier) - a semiconductor that can switch AC loads.
SDLC (Synchronous Data-Link Control) - IBM oriented data flow protocol with error checking.
self-diagnosis - a self check sequence performed by many operation critical devices.
sensitivity - the ability of a system to detect a change.
sensor - a device that is externally connected to survey electrical or mechanical phenomena, and convert
them to electrical or digital values for control or monitoring of systems.
serial communication - elements are sent one after another. This method reduces cabling costs, but typically
also reduces speed, etc.
serial design - is the traditional design method. The steps in the design are performed in serial sequence. For
example, first the geometry is specified, then the analysis is performed, and finally the
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