eBook: Automating Manufacturing Systems; with PLCs


A.3 C

C - A programming language that followed B (which followed A). It has been widely used in software development in the 80s and 90s. It has grown up to become C++ and Java.
CAA (Computer Aided Analysis) - allows the user to input the definition of a part and calculate the performance variables.
cable - a communication wire with electrical and mechanical shielding for harsh environments.
CAD (Computer Aided Design) - is the creation and optimization of the design itself using the computer as a productivity tool. Components of CAD include computer graphics, a user interface, and geometric modelling.
CAD (Computer Aided Drafting) - is one component of CAD which allows the user to input engineering drawings on the computer screen and print them out to a plotter or other device.
CADD (Computer Aided Design Drafting) - the earliest forms of CAD systems were simple electronic versions of manual drafting, and thus are called CADD.
CAE (Computer Aided Engineering) - the use of computers to assist in engineering. One example is the use of Finite Element Analysis (FEA) to verify the strength of a design.
CAM (Computer Aided Manufacturing) - a family of methods that involves computer supported manufacturing on the factory floor.
capacitor - a device for storing energy or mass.
capacitance - referring to the ability of a device to store energy. This is used for electrical capacitors, thermal masses, gas cylinders, etc.
capacity - the ability to absorb something else.
carrier - a high/low frequency signal that is used to transmit another signal.
carry flag - an indication when a mathematical operator has gone past the limitations of the hardware/software.
cascade - a method for connecting devices to increase their range, or connecting things so that they operate in sequence. This is also called chaining.
CASE (Computer Aided Software Engineering) - software tools are used by the developer/programmer to generate code, track changes, perform testing, and a number of other possible functions.
cassette - a holder for audio and data tapes.
CCITT (Consultative Committee for International Telegraph and Telephone) - recommended X25. A member of the ITU of the United Nations.
CD-ROM (Compact Disc Read Only Memory) - originally developed for home entertainment, these have turned out to be high density storage media available for all platforms at very low prices (< $100 at the bottom end). The storage of these drives is well over 500 MB.
CE (Concurrent Engineering) - an engineering method that involves people from all stages of a product design, from marketing to shipping.
CE - a mark placed on products to indicate that they conform to the standards set by the European Common Union.
Celsius - a temperature scale the uses 0 as the freezing point of water and 100 as the boiling point.
centrifugal force - the force on an orbiting object the would cause it to accelerate outwards.
centripetal force - the force that must be applied to an orbiting object so that it will not fly outwards.
channel - an independent signal pathway.
character - a single byte, that when displayed is some recognizable form, such as a letter in the alphabet, or a punctuation mark.
checksum - when many bytes of data are transmitted, a checksum can be used to check the validity of the data. It is commonly the numerical sum of all of the bytes transmitted.
chip - a loose term for an integrated circuit.
chromatography - gases or liquids can be analyzed by how far their constituent parts can migrate through a porous material.
CIM (Computer Integrated Manufacturing) - computers can be used at a higher level to track and guide products as they move through the facility. CIM may or may not include CAD/CAM.
CL (Cutter Location) - an APT program is converted into a set of x-y-z locations stored in a CL file. In turn these are sent to the NC machine via tapes, etc.
clear - a signal or operation to reset data and status values.
client-server - a networking model that describes network services, and user programs.
clipping - the automatic cutting of lines that project outside the viewing area on a computer screen.
clock - a signal from a digital oscillator. This is used to make all of the devices in a digital system work synchronously.
clock speed - the rate at which a computers main time clock works at. The CPU instruction speed is usually some multiple or fraction of this number, but true program execution speeds are loosely related at best.
closed loop - a system that measures system performance and trims the operation. This is also known as feedback. If there is no feedback the system is called open loop.
CMOS (Complimentary Metal Oxide Semi-conductor) - a low power microchip technology that has high noise immunity.
CNC (Computer Numerical Control) - machine tools are equipped with a control computer, and will perform a task. The most popular is milling.
coalescing - a process for filtering liquids suspended in air. The liquid condenses on glass fibers.
coaxial cable - a central wire contains a signal conductor, and an outer shield provides noise immunity. This configuration is limited by its coaxial geometry, but it provides very high noise immunity.
coax - see coaxial cable.
cogging - a machine steps through motions in a jerking manner. The result may be low frequency vibration.
coil - wire wound into a coil (tightly packed helix) used to create electromagnetic attraction. Used in relays, motors, solenoids, etc. These are also used alone as inductors.
collisions - when more than one network client tries to send a packet at any one time, they will collide. Both of the packets will be corrupted, and as a result special algorithms and hardware are used to abort the write, wait for a random time, and retry the transmission. Collisions are a good measure of network overuse.
colorimetry - a method for identifying chemicals using their colors.
combustion - a burning process generating heat and light when certain chemicals are added.
command - a computer term for a function that has an immediate effect, such as listing the files in a directory.
commission - the typical name for getting equipment operational after delivery/installation.
communication - the transfer of data between computing systems.
commutative laws - Booleans algebra laws A+B = B+A and AB=BA.
compare - a computer program element that examines one or more variables, determines equality/inequality, and then performs some action, sometimes a branch.
compatibility - a measure of the similarity of a design to a standard. This is often expressed as a percentage for software. Anything less than 100% is not desirable.
compiler - a tool to change a high level language such as C into assembler.
compliment - to take the logical negative. TRUE becomes false and vice versa.
component - an interchangeable part of a larger system. Components can be used to cut down manufacturing and maintenance difficulties.
compressor - a device that will decrease the volume of a gas - and increase the pressure.
computer - a device constructed about a central instruction processor. In general the computer can be reconfigured (software/firmware/hardware) to perform alternate tasks.
Computer Graphics - is the use of the computer to draw pictures using an input device to specify geometry and other attributes and an output device to display a picture. It allows engineers to communicate with the computer through geometry.
concentric - a shared center between two or more objects.
concurrent - two or more activities occur at the same time, but are not necessarily the same.
concurrent engineering - all phases of the products life are considered during design, and not later during design review stages.
condenser - a system component that will convert steam to water. Typically used in power generators.
conduction - the transfer of energy through some medium.
configuration - a numbers of multifunction components can be connected in a variety of configurations.
connection - a network term for communication that involves first establishing a connection, second data transmission, and third closing the connection. Connectionless networking does not require connection.
constant - a number with a value that should not vary.
constraints - are performance variables with limits. Constraints are used to specify when a design is feasible. If constraints are not met, the design is not feasible.
contact - 1. metal pieces that when touched will allow current to pass, when separated will stop the flow of current. 2. in PLCs contacts are two vertical lines that represent an input, or internal memory location.
contactor - a high current relay.
continuous Noise - a noise that is ongoing, and present. This differentiates from instantaneous, or intermittent noise sources.
continuous Spectrum - a noise has a set of components that are evenly distributed on a spectral graph.
control relay - a relay that does not control any external devices directly. It is used like a variable in a high level programming language.
control variable - a system parameter that we can set to change the system operation.
controls - a system that is attached to a process. Its purpose is to direct the process to some set value.
convection - the transfer of heat energy to liquid or gas that is moving past the surface of an object.
cook's constant - another name for the fudge factor.
core memory - an outdated term describing memory made using small torii that could be polarized magnetically to store data bits. The term lives on when describing some concepts, for example a `core dump' in UNIX. Believe it or not this has not been used for decades but still appears in many new textbooks.
coriolis force - a force that tends to cause spinning in moving frames of reference. Consider the direction of the water swirl down a drain pipe, it changes from the north to the south of the earth.
correction factor - a formal version of the `fudge factor'. Typically a value used to multiply or add another value to account for hard to quantify values. This is the friend of the factor of safety.
counter - a system to count events. This can be either software or hardware.
cps (characters per second) - This can be a good measure of printing or data transmission speed, but it is not commonly used, instead the more confusing `baud' is preferred.
CPU (Central Processing Unit) - the main computer element that examines machine code instructions and executes results.
CRC (Cyclic Redundancy Check) - used to check transmitted blocks of data for validity.
criteria - are performance variables used to measure the quality of a design. Criteria are usually defined in terms of degree - for example, lowest cost or smallest volume or lowest stress. Criteria are used to optimize a design.
crosstalk - signals in one conductor induce signals in other conductors, possibly creating false signals.
CRT (Cathode Ray Tubes) - are the display device of choice today. A CRT consists of a phosphor-coated screen and one or more electron guns to draw the screen image.
crucible - 1. a vessel for holding high temperature materials 2.
CSA (Canadian Standards Association) - an association that develops standards and does some product testing.
CSMA/CD (Carrier Sense Multiple Access with Collision Detection) - a protocol that causes computers to use the same communication line by waiting for turns. This is used in networks such as Ethernet.
CSNET (Computer+Science NETwork) - a large network that was merged with BITNET.
CTS (Clear To Send) - used to prevent collisions in asynchronous serial communications.
current loop - communications that use a full electronic loop to reduce the effects of induced noise. RS-422 uses this.
current rating - this is typically the maximum current that a designer should expect from a system, or the maximum current that an input will draw. Although some devices will continue to work outside rated values, not all will, and thus this limit should be observed in a robust system. Note: exceeding these limits is unsafe, and should be done only under proper engineering conditions.
current sink - a device that allow current to flow through to ground when activated.
current source - a device that provides current from another source when activated.
cursors - are movable trackers on a computer screen which indicate the currently addressed screen position, or the focus of user input. The cursor is usually represented by an arrow, a flashing character or cross-hair.
customer requirements - the qualitative and quantitative minimums and maximums specified by a customer. These drive the product design process.
cycle - one period of a periodic function.
cylinder - a piston will be driven in a cylinder for a variety of purposes. The cylinder guides the piston, and provides a seal between the front and rear of the piston.

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