Globe Valves are named for their spherical body shape with the two halves of the body being separated by an internal baffle. This has an opening that forms a seat onto which a movable plug can be screwed in to close (or shut) the valve. The plug is also called a disc or disk. In globe valves, the plug is connected to a stem which is operated by screw action in manual valves. Typically, automated valves use sliding stems. Automated globe valves have a smooth stem rather than threaded and are opened and closed by an actuator assembly. When a globe valve is manually operated, the stem is turned by a handwheel.

Although globe valves in the past had the spherical bodies which gave them their name, many modern globe valves do not have much of a spherical shape. However, the term globe valve is still often used for valves that have such an internal mechanism. In plumbing, valves with such a mechanism are also often called stop valves since they don’t have the global appearance, but the term stop valve may refer to valves which are used to stop flow even when they have other mechanisms or designs.

Globe valves are used for applications requiring throttling and frequent operation. For example, globe valves or valves with a similar mechanism may be used as sampling valves, which are normally shut except when liquid samples are being taken. Since the baffle restricts flow, they’re not recommended where full, unobstructed flow is required.

Body

The main pressure containing structure of the valve and the most but easily identified as it forms the mass of the valve. It contains all of the valve’s internal parts that will come in contact with the substance being controlled by the valve. The bonnet is connected to the body and provides the containment of the fluid, gas, or slurry that is being controlled.

Globe valves are typically two-port valves, although three port valves are also produced. Ports are openings in the body for fluid flowing in or out. The two ports may be oriented straight across from each other on the body,[5] or oriented at an angle such as a 90° angle. Globe valves with ports at such an angle are called angle globe valves. A globe valve can also have a body in the shape of a y’.

Bonnet

Provides leakproof closure for the valve body. The threaded section of stem goes through a hole with matching threads in the bonnet. Globe valves may have a screw-in, union, or bolted[7] bonnet. Screw-in bonnet is the simplest bonnet, offering a durable, pressure-tight seal. Union bonnet is suitable for applications requiring frequent inspection or cleaning. It also gives the body added strength. A bonnet attached with bolts is used for larger or higher pressure applications. Bonnets also contain the packing, which is a wearable material that maintains the seal between the bonnet and the stem during valve cycling.

The closure member of the valve. Plugs are connected to the stem which is slid or screwed up or down to throttle the flow. Plugs are typically of the balance or unbalanced type. Unbalanced plugs are solid and are used with smaller valves or with low pressure drops across the valve. The advantages are simpler design, with one possible leak path at the seat and usually lower cost. The disadvantages are the limited size; with a large unbalanced plug the forces needed to seat and hold the flow often becomes impractical. Balanced plugs have holes through the plug. Advantages include easier shut off as the plug does not have to overcome static forces. However, a second leak path is created between the plug and the cage, cost is generally higher.

Stem

The stem serves as a connector from the actuator to the inside of the valve and transmits this actuation force. Stems are either smooth for actuator controlled valves or threaded for manual valves. The smooth stems are surrounded by packing material to prevent leaking material from the valve. This packing is a wearable material and will have to be replaced during maintenance. With a smooth stem the ends are threaded to allow connection to the plug and the actuator. The stem must not only withstand a large amount of compression force during valve closure, but also have high tensile strength during valve opening. In addition, the stem must be very straight, or have low run out, in order to ensure good valve closure. This minimum run out also minimizes wear of the packing contained in the bonnet, which provides the seal against leakage. The stem may be provided with a shroud over the packing nut to prevent foreign bodies entering the packing material, which would accelerate wear.

Cage

The cage is part of the valve that surrounds the plug and is located inside the body of the valve. Typically, the cage is one of the greatest determiners of flow within the valve. As the plug is moved more of the openings in the cage are exposed and flow is increased and vice versa. The design and layout of the openings can have a large effect on flow of material (the flow characteristics of different materials at temperatures, pressures that are in a range). Cages are also used to guide the plug to the seat of the valve for a good shutoff, substituting the guiding from the bonnet.

Seat ring

The seat ring provides a stable, uniform and replaceable shut off surface. Seat rings are usually held in place by pressure from the fastening of the bonnet to the top of the body. This pushes the cage down on the lip of the seat ring and holds it firmly to the body of the valve. Seat rings may also be threaded and screwed into a thread cut in the same area of the body. However this method makes removal of the seat ring during maintenance difficult if not impossible. Seat rings are also typically beveled at the seating surface to allow for some guiding during the final stages of closing the valve.

Economical globe valves or stop valves with a similar mechanism used in plumbing often have a rubber washer at the bottom of the disc for the seating surface, so that rubber can be compressed against the seat to form a leak-tight seal when shut.

Materials

Typically globe valves are made of metallic alloys, although some synthetic materials are available. These materials are chosen based on pressure, temperature, controlled media properties. Corrosive and/or erosive process streams may require a compromise in material selection or exotic alloys or body coatings to minimize these material interactions and extend the life of the valve or valve trim components. Typically, carbon steel alloys are specified for noncorrosive applications. Other alloys such as Hastelloy, Monel, Inconel and others are available.

Packing material must also be considered during valve selection. Typically the requirement for a low friction packing conflict with a durable material that will provide low maintenance requirements during service life. Corrosive applications can further complicate packing material selection as the typical packing materials may or may not be compatible with the processed materials. Typically graphite or PTFE is used due to its low friction coefficient. Enviro-seal applications also have the availablilty of constant applied force (live-load) packing. While more complex, it allows for constant packing force load throughout the life of the packing material. This packing helps meet contemporary environmental laws.

(text and images courtesy of Wikipedia)

Related posts:

1. Ball Valve

Ball valves are used extensively in industry because they are very versatile, supporting pressures up to 10,000 psi and temperatures up to 200 Deg C. Sizes from 1/4″ to 12″ are readily available. They are easy to repair, and operate manually or by actuators.

The body of ball valves may be made of metal, plastic or metal with a ceramic center. The ball is often chrome plated to make it more durable.
[edit] Types of ball valve

Types of Ball Valves

There are five general body styles of ball valves: single body, three piece body,split body, top entry, and welded.

There are three general types of ball valves according to bore

* A full port ball valve has an over sized ball so that the hole in the ball is the same size as the pipeline resulting in lower friction loss. Flow is unrestricted, but the valve is larger. This is not required for general industrial applications as all types of Valves used in industry like Gate Valves, Plug Valves, Butterfly valves etc have restrictions across the flow and does not permit full flow. This leads to excessive costs for full bore ball valves and is genearlly a unneccessary spending for customers.

* In reduced port ball valves, flow through the valve is one pipe size smaller than the valve’s pipe size resulting in flow area becoming lesser than pipe. But the flow discharge remains constant as it is a Multipler factor of Flow discharge(Q) is equal to Area of Flow (A) into Velocity (V). A1V1=A2V2 i.e the Velocity increase with reduced Area of flow and Velocity decreases with increased area of flow.

* A V port ball valve has either a ‘v’ shaped ball or a ‘v’ shaped seat. This allows the orifice to be opened and closed in a more controlled manner with a closer to linear flow characteristic. When the valve is in the closed position and opening is commenced the small end of the ‘v’ is opened first allowing stable flow control during this stage. This type of design requires a generally more robust construction due to higher velocities of the fluids, which would quickly damage a standard valve.

* A trunnion ball valve has a mechanical means of anchoring the ball at the top and the bottom, this design is usually applied on larger and higher pressure valves (say, 4″ and above 600 psi and above).

Manually operated ball valves can be closed quickly and thus there is a danger of water hammer. Some ball valves are equipped with an actuator that may be pneumatically or motor (electric) operated. These valves can be used either for on/off or flow control. A pneumatic flow control valve is also equipped with a positioner which transforms the control signal into actuator position and valve opening accordingly.

Related posts:

1. Globe Valve

American Institute of Aeronautics and Astronautics

American Society of Mechanical Engineers

American Institute of Chemical Engineers

Architectural Engineering Institute

Biomedical Engineering Society

Institute of Electrical and Electronics Engineers

Society of Petroleum Engineers

Related posts:

1. Top Ten Engineering Colleges
2. Engineering Information Sites

But the reality of life in the technical world is that, first, you have to get a job. Getting a job as an engineer starts first with getting the attention of a potential employer and that is where a professional resume comes into play.

I want to give you a couple of resume writing tips before you start writing a resume. You will have to do some research to find what keywords are appropriate and pertinent to your field.

Resume Keywords Rule

Look at the online postings for engineering jobs. Find all of the keywords that apply to you and your experience, such as PLC, motors, drives, automation and so on. Make a list of these before you start writing a resume.

Don’t worry about the format of the resume at this stage. A simple list is fine.

Most resumes are placed online and recruiters and companies search for keywords first. It won’t do you any good to have a beautiful resume format if your resume never shows up in the searches.

Next, make a list of your skills and abilities. Use your keywords.

After that, list all of your previous employers in reverse chronological order. Make sure the dates are accurate. Under each employer, list what duties you performed. Again, use your keywords. Don’t be too humble here; I have found that most of the resumes I have reviewed understate the applicant’s ability.

How To Write A Resume The Easy Way – Use A Resume Writing Service To Create A Professional Resume

At this point, you can make a decision. You can choose to write your resume yourself, using eloquent phrases that flow trippingly off the tongue and impress the potential employer with your extensive knowledge of the English language.

Get Resume Help and Resume Tips

Or, you can hire a professional resume writing service to make a good, solid advertisement for you. They can provide the resume help you need.

After all, a resume is an advertisement; we don’t want to forget that. Unless you have experience in advertising, you will probably be much further ahead by paying someone else for his or her expertise in this matter.

You wouldn’t have to worry about the resume format, getting help with your resume, searching online for resume tips or some free resume template.

These people are writers and they do this for a living. Granted, there are quite a few companies on the Internet that claim to be able to write resumes, but based on some their websites, I have my doubts.

I ran across a company called ResumeWriters.com. Their website looks really sharp, modern and businesslike. Their copy is crisp and concise. They even guarantee that the resume they right for you will land you an interview in 30 days or they will rewrite it for you.

They have a number of sample resumes online from electrician to optical engineer.

Their prices are very reasonable, especially when you consider that the basic resume format and structure won’t change for a few years. That means you probably won’t have to hire another resume service for a long time

Take a look at resumewriters.com here.

Best of luck!

Related posts:

1. Writing A Good Objective Statement For Your Resume
2. Sample Resume

Learn Who You Can Trust to Provide Accurate Information
Gathering accurate information is an important aspect of troubleshooting. However well meaning, some of the people you deal with will not provide accurate information. This may seem like stating the obvious, but always try to verify all the information you are given.

Never Compromise The Safety Of The Machine Or The Workers
Many times when you are charged with troubleshooting a system, you are placed in a position of authority. Be aware that others will look to you to provide direction. Make sure that as you provide that direction, you are giving their personal safety your highest priority.

Listen to Your Boss
If he tells you to call a vendor, don’t fiddle around with trying to fix it yourself – call the vendor.

Don’t Let Your Ego Get in the Way
Your job is to fix the equipment. If it means making a phone call to someone you dislike, admitting that you made a mistake in your initial diagnosis, just do it and get over it. In the long run, it is the easy way.

Communication
Keep the lines of communication open. Network with people who may be valuable to you when you’re trying to troubleshoot a system. Keep those who have an interest in the system well informed of problems you discover or changes you make to the system.

It Is Not Necessarily About Knowing One PLC Or Another – It Is About Understanding The Troubleshooting Method
All PLCs are different. All systems are different. The real key to being a good troubleshooter is to understand the Troubleshooting Method.

First, try to understand how to troubleshoot anything and let your method be refined as you gain experience.

DO NOT Compromise The Safety Of A Machine By Altering The Program
Before you make any changes to the program, always ask yourself if this change will affect the safety of the machine or the people who work around it.

No One Expects You To Wave A Magic Wand
No one expects you to wave a magic wand and get the machine to work. What is expected, however, is that you have a goal and a plan, and that you are executing the plan. It is true that, many times, there is pressure in a troubleshooting scenario.

Don’t be nervous; present a blend of humility and confidence. In other words, respect what information is given to you, but be prepared to make your own decisions regarding how to proceed with the troubleshooting.

Know When To Stop
Don’t go past the mark you aimed for; know when to stop.

That moment of victory is often the moment of greatest peril. When you have solved the initial problem, and you are the hero, arrogance and overconfidence can push you past the goal you had aimed for. By going too far, you make new problems for yourself.  Don’t allow success to go to your head.  Remember that there is no substitute for strategy and careful planning. Set a goal, and when you reach it, stop.

Related posts:

1. Troubleshooting – Make Sure You Have a Clear Goal and a Concise Plan
2. Troubleshooting A PLC With RSLogix 5000

Related posts:

1. Industrial Automation Glossary – Q, R
2. Industrial Automation Glossary – C
3. Industrial Automation Glossary – B

1 a logic positive, high, or 1.

A/D Analog to digital converter (see ADC).

abort the disruption of normal operation.

absolute pressure a pressure measured relative to zero pressure.

absorptive law a special case of Boolean algebra where A(A+B) becomes A.

absorption loss
when sound or vibration energy is lost in a transmitting or reflecting medium. This is the result of generation of other forms of energy such as heat.

AC (Alternating Current)
most commonly an electrical current and voltage that changes in a sinusoidal pattern as a function of time. It is also used for voltages and currents that are not steady (DC). Electrical power is normally distributed at 60Hz or 50Hz.

AC contactor
a contactor designed for AC power.

acceptance test
a test for evaluating a newly purchased system’s performance, capabilities, and conformity to specifications, before accepting, and paying the supplier.

accumulator
a temporary data register in a computer CPU.

accuracy
the difference between an ideal value and a physically realizable value.

acidity
a solution that has an excessive number of hydrogen atoms. Acids are normally corrosive.

acknowledgement (ACK)
a response that indicates that data has been transmitted correctly.

acoustic
another term for sound.

actuator
a device that when activated will result in a mechanical motion. For example a motor, a solenoid valve, etc.

ADC (Analog to Digital Converter)
a circuit that will convert an analog voltage to a digital value, also referred to as A/D.

ADCCP (Advanced Data Communications Procedure)
ANSI standard for synchronous communication links with primary and secondary functions.

address
a code (often a number) that specifies a location in a computers memory.

address register
a pointer to memory locations.

adsorption
the ability of a material or apparatus to adsorb energy.

agitator
causes fluids or gases to mix.

AI (Artificial Intelligence)
the use of computer software to mimic some of the cognitive human processes.

algorithms
a software procedure to solve a particular problem.

aliasing
in digital systems there are natural limits to resolution and time that can be exceeded, thus aliasing the data. For example. an event may happen too fast to be noticed, or a point may be too small to be displayed on a monitor.

alkaline
a solution that has an excess of HO pairs will be a base. This is the compliment to an acid.

alpha rays
ions that are emitted as the result of atomic fission or fusion.

alphanumeric
a sequence of characters that contains both numbers and letters.

ALU (Arithmetic Logic Unit)
a part of a computer that is dedicated to mathematical operations.

AM (Amplitude Modulation)
a fixed frequency carrier signal that is changed in amplitude to encode a change in a signal.

ambient
normal or current environmental conditions.

ambient noise
a sort of background noise that is difficult to isolate, and tends to be present throughout the volume of interest.

ambient temperature
the normal temperature of the design environment.

analog signal
a signal that has continuous values, typically voltage.

analysis
the process of review to measure some quality.

and
a Boolean operation that requires all arguments to be true before the result is true.

annealing
heating of metal to relieve internal stresses. In many cases this may soften the material.

annotation
a special note added to a design for explanatory purposes.

ANSI (American National Standards Institute)
a developer of standards, and a member of ISO.

APF (All Plastic Fiber cable)
fiber optic cable that is made of plastic, instead of glass.

API (Application Program Interface)
a set of functions, and procedures that describes how a program will use another service/library/program/etc.

application
the task which a tool is put to, This normally suggests some level of user or real world interaction.

application layer
the top layer in the OSI model that includes programs the user would run, such as a mail reader.

APT (Automatically Programmed Tools)
a language used for directing computer controlled machine tools.

arc
when the electric field strength exceeds the dielectric breakdown voltage, electrons will flow.

architecture
the general layout or design at a higher level.

armature
the central rotating portion of a DC motor or generator, or a moving part of a relay.

ARPA (Advanced Research Projects Agency)
now DARPA. Originally funded ARPANET.

ASCII (American Standard Code for Information Interchange)
a set of numerical codes that correspond to numbers, letters, special characters, and control codes.

aspirator
a device that moves materials with suction.

assembler
converts assembly language into machine code.

assembly language
a mnemonic set of commands that can be directly converted into commands for a CPU.

associative dimensioning
a method for linking dimension elements to elements in a drawing.

associative laws
Boolean algebra laws A+(B+C) = (A+B)+C or A(BC) = (AB)C

asynchronous
events that happen on an irregular basis, and are not predictable.

asynchronous communications (serial)
strings of characters (often ASCII) are broken down into a series of on/off bits. These are framed with start/stop bits, and parity checks for error detection, and then send out one character at a time. The use of start bits allows the characters to be sent out at irregular times.

attenuation
to decrease the magnitude of a signal.

attenuation
as the sound/vibration energy propagates, it will undergo losses. The losses are known as attenuation, and are often measured in dB. For general specifications, the attenuation may be tied to units of dB/ft.

attribute
a nongraphical feature of a part, such as color.

audible range
the range of frequencies that the human ear can normally detect from 16 to 20,000 Hz.

automated
a process that operates without human intervention.

automatic control
a feedback of a system state is compared to a desired value and the control value for the system is adjusted by electronics, mechanics and/or computer to compensate for differences.

auxiliary power
secondary power supplies for remote or isolated systems.

AWG (American Wire Gauge)
specifies conductor size. As the number gets larger, the conductors get smaller.

Related posts:

1. Industrial Automation Glossary – S
2. Industrial Automation Glossary – Q, R
3. Industrial Automation Glossary – N, O, P

background
in multitasking systems, processes may be running in the background while the user is working in the foreground, giving the user the impression that they are the only user of the machine (except when the background job is computationally intensive).

background suppression
the ability of a sensing system to discriminate between the signal of interest, and background noise or signals.

backplane
a circuit board located at the back of a circuit board cabinet. The backplane has connectors that boards are plugged into as they are added.

backup
a redundant system to replace a system that has failed.

backward chaining
an expert system looks at the results and looks at the rules to see logically how to get there.

band pressure Level
when measuring the spectrum of a sound, it is generally done by looking at frequencies in a certain bandwidth. This bandwidth will have a certain pressure value that is an aggregate for whatever frequencies are in the bandwidth.

base
1. a substance that will have an excess of HO ions in solution form. This will react with an acid. 2. the base numbering system used. For example base 10 is decimal, base 2 is binary

baseband
a network strategy in which there is a single carrier frequency, that all connected machines must watch continually, and participate in each transaction.

BASIC
(Beginner’s All Purpose Symbolic Instruction Code)

batch processing
an outdated method involving running only one program on a computer at once, sequentially. The only practical use is for very intensive jobs on a supercomputer.

battery backup
a battery based power supply that keeps a computer (or only memory) on when the master power is off.

BAUD
The maximum number of bits that may be transmitted through a serial line in one second. This also includes some overhead bits.

BCC (Block Check Character)
a character that can check the validity of the data in a block.

BCD (Binary Coded Decimal)
numerical digits (0 to 9) are encoded using 4 bits. This allows two numerical digits to each byte.

beam
a wave of energy waves such as light or sound. A beam implies that it is not radiating in all directions, and covers an arc or cone of a few degrees.

bearing
a mechanical support between two moving surfaces. Common types are ball bearings (light weight) and roller bearings (heavy weight), journal bearings (rotating shafts).

beats
if two different sound frequencies are mixed, they will generate other frequencies. if a 1000Hz and 1001Hz sound are heard, a 1Hz (=1000

benchmark
a figure to compare with. If talking about computers, these are often some numbers that can be use to do relative rankings of speeds, etc. If talking about design, we can benchmark our products against our competitors to determine our weaknesses.

Bernoulli’s principle
a higher fluid flow rate will result in a lower pressure.

beta ratio
a ratio of pipe diameter to orifice diameter.

beta rays
electrons are emitted from a fission or fusion reaction.

beta site
a software tester who is actually using the software for practical applications, while looking for bugs. After this stage, software will be released commercially.

big
endian

binary
a base 2 numbering system with the digits 0 and 1.

binary
specifies a number system that has 2 digits, or two states.

binary number
a collection of binary values that allows numbers to be constructed. A binary number is base 2, whereas normal numbering systems are base 10.

BIOS (Basic Input Output System)
a set of basic system calls for accessing hardware, or software services in a computer. This is typically a level lower than the operating system.

bit
a single binary digit. Typically the symbols 0 and 1 are used to represent the bit value.

bit/nibble/byte/word
binary numbers use a 2 value number system (as opposed to the decimal 0

BITNET (Because It’s Time NET)
An academic network that has been merged with CSNET.

blackboard
a computer architecture when different computers share a common memory area (each has its own private area) for sharing/passing information.

blast furnace
a furnace that generates high temperatures by blowing air into the combustion.

bleed nozzle
a valve or nozzle for releasing pressure from a system.

block
a group of bytes or words.

block diagram
a symbolic diagram that illustrates a system layout and connection. This can be used for analysis, planning and/or programming.

block diagrams
a special diagram for illustrating a control system design.

BOC (Bell Operating Company)
there are a total of 7 regional telephone companies in the U.S.A.

boiler
a device that will boil water into steam by burning fuel.

BOM (Bills Of Materials)
list of materials needed in the production of parts, assemblies, etc.

Boolean
a system of numbers based on logic, instead of real numbers. There are many similarities to normal mathematics and algebra, but a separate set of operators, axioms, etc. are used.

bottom
up design

bounce
switch contacts may not make absolute contact when switching. They make and break contact a few times as they are coming into contact.

Bourdon tube
a pressure tube that converts pressure to displacement.

BPS (Bits Per Second)
the total number of bits that can be passed between a sender and listener in one second. This is also known as the BAUD rate.

branch
a command in a program that can cause it to start running elsewhere.

bread board
a term used to describe a temporary electronic mounting board. This is used to prototype a circuit before doing final construction. The main purpose is to verify the basic design.

breadth first search
an AI search technique that examines all possible decisions before making the next move.

breakaway torque
the start

breakdown torque
the maximum torque that an AC motor can produce at the rated voltage and frequency.

bridge
1. an arrangement of (typically 4) balanced resistors used for measurement. 2. A network device that connects two different networks, and sorts out packets to pass across.

broad
band noise

broadband networks
multiple frequencies are used with multiplexing to increase the transmission rates in networks.

broadcast
a network term that describes a general broadcast that should be delivered to all clients on a network. For example this is how Ethernet sends all of its packets.

brush
a sliding electrical conductor that conducts power to/from a rotor.

BSC (Binary Synchronous Communication)
a byte oriented synchronous communication protocol developed by IBM.

BSD (Berkeley Software Distribution)
one of the major versions of UNIX.

buffer
a temporary area in which data is stored on its way from one place to another. Used for communication bottlenecks and asynchronous connections.

bugs
hardware or software problems that prevent desired components operation.

burner
a term often used for a device that programs EPROMs, PALs, etc. or a bad cook.

bus
a computer has buses (collections of conductors) to move data, addresses, and control signals between components. For example to get a memory value, the address value provided the binary memory address, the control bus instructs all the devices to read/write, and to examine the address. If the address is valid for one part of the computer, it will put a value on the data bus that the CPU can then read.

byte
an 8 bit binary number. The most common unit for modern computers.

Related posts:

1. Industrial Automation Glossary – A
2. Industrial Automation Glossary – J, K, L, M
3. Industrial Automation Glossary – N, O, P

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 modeling.

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.

capacitance
referring to the ability of a device to store energy. This is used for electrical capacitors, thermal masses, gas cylinders, etc.

capacitor
a device for storing energy or mass.

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.

cassette
a holder for audio and data tapes.

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

clear
a signal or operation to reset data and status values.

client
server

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)

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.

coax
see coaxial cable.

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.

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.

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

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.

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.

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

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

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

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

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.

Related posts:

1. Industrial Automation Glossary – N, O, P
2. Industrial Automation Glossary – B
3. Industrial Automation Glossary – A

DARPA (Defense Advanced Research Projects Agency)

data acquisition
refers to the automated collection of information collected from a process or system.

data highway
a term for a communication bus between two separated computers, or peripherals. This term is mainly used for PLC’s.

data link layer
an OSI model layer

data logger
a dedicated system for data acquisition.

data register
stores data values temporarily in a CPU.

database
a software program that stores and recalls data in an organized way.

DC (Direct Current)
a current that flows only in one direction. The alternative is AC.

DCA (Defense Communications Agency)
developed DDN.

DCD (Data Carrier Detect)
used as a handshake in asynchronous communication.

DCE (Data Communications Equipment)
A term used when describing unintelligent serial communications clients. An example of this equipment is a modem. The complement to this is DTE.

DCE (Distributed Computing Environment)
applications can be distributed over a number of computers because of the use of standards interfaces, functions, and procedures.

DDN (Defense Data Network)
a group of DoD networks, including MILNET.

dead band
a region for a device when it no longer operates.

dead time
a delay between an event occurring and the resulting action.

debounce
a switch may not make sudden and complete contact as it is closes, circuitry can be added to

debug
after a program has been written it undergoes a testing stage called debugging that involves trying to locate and eliminate logic and other errors.

decision support
the use of on

DECnet (Digital Equipment Corporation net)
a proprietary network architecture developed by DEC. decrement

dedicated computer
a computer with only one task.

default
a standard condition.

demorgan’s laws
Boolean laws great for simplifying equations ~(AB) = ~A + ~B, or ~(A+B) = ~A~B.

density
a mass per unit volume.

depth first search
an artificial intelligence technique that follows a single line of reasoning first.

derivative control
a control technique that uses changes in the system of setpoint to drive the system. This control approach gives fast response to change.

design
creation of a new part/product based on perceived needs. Design implies a few steps that are ill defined, but generally include, rough conceptual design, detailed design, analysis, redesign, and testing.

design capture
the process of formally describing a design, either through drafted drawings, schematic drawings, etc.

design cycle
the steps of the design. The use of the word cycle implies that it never ends, although we must at some point decide to release a design.

design Variables
are the parameters in the design that describe the part. Design variables usually include geometric dimensions, material type, tolerances, and engineering notes.

detector
a device to determine when a certain condition has been met.

device driver
controls a hardware device with a piece of modular software.

DFA (Design For Assembly)
a method that guides product design/redesign to ease assembly times and difficulties.

DFT (Design for Testability)
a set of design axioms that generally calls for the reduction of test steps, with the greatest coverage for failure modes in each test step.

diagnostic
a system or set of procedures that may be followed to identify where systems may have failed. These are most often done for mission critical systems, or industrial machines where the user may not have the technical capability to evaluate the system.

diaphragm
used to separate two materials, while allowing pressure to be transmitted.

differential
refers to a relative difference between two values. Also used to describe a calculus derivative operator.

differential amplifier
an amplifier that will subtract two or more input voltages.

diffuse field
multiple reflections result in a uniform and high sound pressure level.

digital
a system based on binary on

diode
a semiconductor device that will allow current to flow in one direction.

DIP switches
small banks of switches designed to have the same footprint as an integrated circuit.

distributed
suggests that computer programs are split into parts or functions and run on different computers

distributed system
a system can be split into parts. Typical components split are mechanical, computer, sensors, software, etc.

DLE (Data Link Escape)
An RS

DMA (Direct Memory Access)
used as a method of transferring memory in and out of a computer without slowing down the CPU.

DNS (Domain Name System)
an internet method for name and address tracking.

documentation
one or more documents that instruct in the use, installation, setup, maintenance, troubleshooting, etc. for software or machinery. A poor design supported by good documentation can often be more useful than a good design unsupported by poor documentation.

domain
the basic name for a small or large network.

doppler shift
as objects move relative to each other, a frequency generated by one will be perceived at another frequency by the other.

DOS (Disk Operating System)
the portion of an operating system that handles basic I/O operations. The most common example is Microsoft MS

dotted decimal notation
the method for addressing computers on the internet with IP numbers such as ‚Äò129.100.100.13′.

double pole
a double pole switch will allow connection between two contacts. These are useful when making motor reversers. see also single pole.

double precision
a real number is represented with 8 bytes (single precision is 4) to give more precision for calculations.

double throw
a switch or relay that has two sets of contacts.

download
to retrieve a program from a server or higher level computer.

downtime
a system is removed from production for a given amount of downtime.

drag
a force that is the result of a motion of an object in a viscous fluid.

drop
a term describing a short connection to peripheral I/O.

drum sequencer
a drum has raised/lowered sections and as it rotates it opens/closes contacts and will give sequential operation.

dry contact
an isolated output, often a relay switched output.

DSP (Digital Signal Processor)
a medium complexity micro-controller that has a build in floating point unit. These are very common in devices such as modems.

DSR (Data Set Ready)
used as a data handshake in asynchronous communications.

DTE (Data Terminal Equipment)
a serial communication line used in RS

DTR (Data Terminal Ready)
used as a data handshake in asynchronous communications to indicate a listener is ready to receive data.

dump
a large block of memory is moved at once (as a sort of system snapshot).

duplex
serial communication that is in both directions between computers at the same time.

dynamic braking
a motor is used as a brake by connecting the windings to resistors. In effect the motor becomes a generator, and the resistors dissipate the energy as heat.

dynamic variable
a variable with a value that is constantly changing.

dyne
a unit of force

Related posts:

1. Industrial Automation Glossary – B
2. Glossary – E, F
3. Industrial Automation Glossary – C