Glossary – E, F
Written by Neal Babcock
eccentric
two or more objects do not have a common center.
echo
a reflected sound wave.
eddy currents
small currents that circulate in metals as currents flow in nearby conductors. Generally unwanted.
EEPROM
Electrically Erasable Programmable Read Only Memory.These chips can be erased and programmed while in use with a computer, and store memory that is not sensitive to power.
effective sound pressure
the RMS pressure value gives the effective sound value for fluctuating pressure values. This value is some fraction of the peak pressure value.
EIA (Electronic Industries Association)
A common industry standards group focusing on electrical standards.
electro
optic isolator
electromagnetic
a broad range term refering to magnetic waves. This goes from low frequency signals such as AM radio, up to very high frequency waves such as light and X
electrostatic
devices that used trapped charge to apply forces and caused distribution. An example is droplets of paint that have been electrically charged can be caused to disperse evenly over a surface that is oppositely charged.
electrostatics discharge
a sudden release of static electric charge (in non-grounded systems). This can lead to uncomfortable electrical shocks, or destruction of circuitry.
EMI (ElectroMagnetic Interference)
transient magnetic fields cause noise in other systems.
emulsify
to mix two materials that would not normally mix. for example an emulsifier can cause oil and water to mix.
enable
a digital signal that allows a device to work.
encoding
a conversion between different data forms.
energize
to apply power to a circuit or component.
energy
the result of work. This concept underlies all of engineering. Energy is shaped, directed and focused to perform tasks.
engineering work stations
are self contained computer graphics systems with a local CPU which can be networked to larger computers if necessary. The engineering work station is capable of performing engineering synthesis, analysis, and optimization operations locally.
EOH (End of Header)
A code in a message header that marks the end of the header block.
EOT (End Of Transmission)
an ASCII code to indicate the end of a communications.
EPROM (ELECTRICALLY Programmable Read Only Memory)
A program can be written to this memory using a special programmer, and erased with ultraviolet light. After a program is written, it does not require power for storage.
error signal
a control signal that is the difference between a desired and actual position.
ESD
see electrostatic discharge.
esters
a chemical that was formed by a reaction between alcohol and an acid.
ETX (End Of Text)
a marker to indicate the end of a text block in data transmission.
even parity
a checksum bit used to verify data in other bits of a byte.
execution
when a computer is under the control of a program, the program is said to be executing.
expansion principle
when heat is applied a liquid will expand.
fail safe
a design concept where system failure will bring the system to an idle or safe state.
Faraday’s electromagnetic induction law
if a conductor moves through a magnetic field a current will be induced. The angle between the motion and the magnetic field needs to be 90 deg for maximum current.
Fahrenheit
a temperature system that has 180 degrees between the freezing and boiling point of water.
fatal error
an error so significant that a software/hardware cannot continue to operate in a reliable manner.
fault
a small error that may be recoverable, or may result in a fatal error.
FCS (Frame Check Sequence)
data check flag for communications.
FDDI (Fiber Distributed Data Interface)
a fiber optic token ring network scheme in which the control tokens are counter rotating.
FDX (Full Duplex)
all characters that are transmitted are reflected back to the sender.
FEA (Finite Element Analysis)
is a numerical technique in which the analysis of a complex part is subdivided into the analysis of small simple subdivisions.
feedback
a common engineering term for a system that examines the output of a system and uses is to tune the system. Common forms are negative feedback to make systems stable, and positive feedback to make systems unstable.
fetch
when the CPU gets a data value from memory.
fiber optics
data can be transmitted by switching light on/off, and transmitting the signal through an optical fiber. This is becoming the method of choice for most long distance data lines because of the low losses and immunity to EMI.
FIFO (First In First Out)
items are pushed on a stack. The items can then be pulled back off last first.
file
a concept of a serial sequence of bytes that the computer can store information in, normally on the disk. This is a ubiquitous concept, but file is also used by Allen Bradley to describe an array of data.
filter
a device that will selectively pass matter or energy.
firmware
software stored on ROM (or equivalent).
flag
a single binary bit that indicates that an event has/has not happened.
flag
a single bit variable that is true or not. The concept is that if a flag is set, then some event has happened, or completed, and the flag should trigger some other event.
flame
an email, or net news item that is overtly critical of another user, or an opinion. These are common because of the ad
flange
a thick junction for joining two pipes.
floating point
uses integer math to represent real numbers.
flow chart
a schematic diagram for representing program flow. This can be used during design of software, or afterwards to explain its operation.
flow meter
a device for measuring the flow rate of fluid.
flow rate
the volume of fluid moving through an area in a fixed unit of time.
fluorescence
incoming UV light or X
force
a PLC output or input value can be set on artificially to test programs or hardware. This method is not suggested.
format
1. a physical and/or data structure that makes data re-readable, 2. the process of putting a structure on a disk or other media.
forward chaining
an expert system approach to examine a set of facts and reason about the probable outcome.
fragmentation
the splitting of an network data packet into smaller fragments to ease transmission.
frame buffers
store the raster image in memory locations for each pixel. The number of colors or shades of gray for each pixel is determined by the number of bits of information for each pixel in the frame buffer.
free field
a sound field where none of the sound energy is reflected.
frequency
the number of cycles per second for a sinusoidally oscillating vibration/sound.
friction
the force resulting from the mechanical contact between two masses.
FSK (Frequency Shift Keying)
uses two different frequencies, shifting back and forth to transmit bits serially.
FTP (File Transfer Protocol)
a popular internet protocol for moving files between computers.
fudge factor
a number that is used to multiply or add to other values to make the experimental and theoretical values agree.
full duplex
a two way serial communication channel can carry information both ways, and each character that is sent is reflected back to the sender for verification.
fuse
a device that will destruct when excessive current flows. It is used to protect the electrical device, humans, and other devices when abnormally high currents are drawn. Note: fuses are essential devices and should never be bypassed, or replaced with fuses having higher current rating.
