red value and the true value of the measured variable. Notes: 1. The error is positive when the measured va lue is greater than the true value. Error = (measured value) – (true value). 2. When giving the error in the data sheet of an instrument or device, the kind of cali bration of the instrument or device has to be specified.
2. A discrepancy between a computed, observed or
measured value or condition and the true, specified or theoretically correct value or condition.
error analysis (software) The process of investiga ting an observed software fault with the purpose of tracking the fault to its source.
error band (electrical transducers) The band of maximum deviations of output values from a specified reference line or curve due to those causes attributable to the transducer.
error burst In data transmission, a sequence of sig nals containing one or more errors but counted as only one unit in accordance with some specific criterion or measure.
error category One of a set of classes into which an error, fault, or failure might fall. Categories may be defined for the cause, criticality, effect, life cycle pha se when introduced or detected, or other characteris tics of the error, fault, or failure.
error checking Data quality assurance usually at- tempted by calculating some property of the data block before transmission. The resulting property or check character is also sent to the receiver, where it may be inspected and compared with a recalculated value based on the received data.
error code 1. A specific character that may be pun
ched into a card or tape to indicate that a conscious er ror was made in the associated block of data. Machi nes reading the error code may be programmed to throw out the entire block automatically. 2. Illegal control code on a binary code.
error control That part of a protocol controlling the detection, and possibly the correction of errors.
error control commands The ideal communication computer will have special commands for generating longitudinal redundancy check characters, cyclic re dundancy checks, and vertical redundancy checks. These special commands will perform these functions in a fraction of the time that would be required with a general purpose instruction set.
error control restart procedure Checkpoints and restart procedures make it possible, in the event of an error in interruption, to continue processing from the last checkpoint rather than from the beginning of the computer run.
error control software Software that monitors a computer system to detect, record and possibly to cor rect errors.
error correcting code An error-detecting code de- signed to allow for the automatic correction of certain types of error.
error correction 152 ETFE error correction A method used to correct erroneous
data produced during data transmission, transfer, or storage.
error-correction routine A series of computer ins tructions programmed to correct a detected error con dition.
error curve See calibration curve.
error detecting and feedback system A system employing an error-detecting code and so arranged that a character or block detected as being in error au tomatically initiates a request for retransmission of the signal detected as being in error.
error-detecting code, self-checking code A code in which each coded representation conforms to specific rules of construction so that their violation in dicates the presence of errors.
error detection 1. System which detects errors occa
sioned by transmission equipment or facilities. 2. A method of determining whether data has been trans mitted or transferred incorrectly. 3. A method of pro cessing data such that if transmission or processing errors occur, false results are discovered. Refers to Honeywell TDC 3 000 control systems.
error detection routine A routine used to detect wheather or not an error has occured, usually without special provision to find or indicate its location.
error dump The dumping onto tape, etc. by a priority program of information and core storage so that the cause of an equipment or program error interrupt may be assessed by the analysts.
error list A list created by a compiler indicating in- correct or invalid instructions in a source program.
error message An indication that an error has been detected.
error model A mathematical model used to predict or estimate the number of remaining faults, reliability, required test time, or similar characteristics of a soft- ware system. See also error prediction.
(of indication)
error (of indication) of a measuring instrument
The indication of a measuring instrument minus the (conventional) true value of the measurand. Note: For a material measure, the indication is its nominal or marked value.
error variable Difference between the reference vari able and the feedback variable.
(absolute) error of measurement The result of a measurement minus the (conventional) true value of the measurand. Notes: 1. The term relates equally to: the indication, the uncorrected result, the corrected re sult. 2. The know parts of the error of measurement may be compensated by applying appropriate correc tions. The error of the corrected result can only be characterized by an uncertainty. 3. “Absolute error“, which has a sign, should not be confused with absolu te value of an error which is the modulus of an error.
error prediction A quantitative statement about the expected number or nature of software problems, faults, or failures in a software system. See also error model.
error prediction model See error model.
error range 1. The set of values that an error may ta
ke. 2. See error span.
error rate The ratio of the total number of errors de tected to the total amount of data transmitted or trans ferred.
error-rate damping A damping method in which a signal proportional to the rate of change of error is ad ded to the error signal for anticipatory purposes.
error ratio 1. The ratio of the number of data units in
error to the total number of data units. 2. Same as de viation ratio.
error recovery The process of correcting or bypas sing the effect of a fault to restore a computer system to a prescribed condition.
error seeding See fault seeding.
error signal Output signal of a comparing element of a closed loop control system.
error span (error range deprecated in this sen se) The difference between the highest and the lowest error values.
error squared The technique of squaring the error in a linear control action to produce a nonlinear correc tion.
error voltage A voltage which is present in a servo system when the input and output shafts are not in correspondence. The error voltage, which actuates the servo system, is proportional to the angular displace ment between the two shafts.
Es Chemical symbol for Einsteinium.
escutcheon, escutcheon plate A decorative shield, flange, or border around a panel-mounted part such as a dial or control knob.
ESD Static Electricity Discharge = Electrostatic Discharge. See electrostatic discharge.
ESDI Enhanced Small Device Interface. An interface against hard disks.
ESD test generator Instrument used in electrostatic discharge testing. See further IEC standard 801-2; Part 2: Electrostatic discharge requirements.
ESF European Science Foundation.
ESITB Electricity Supply Industry Training Board (GB).
ESONE European Standards of Nuclear Electronics. Part of IEC.
esparto pulp Pulp manufactured from esparto grass or similar steppe grass.
ESR See electroslag remelting furnace.
ESRIN European Space Research Institute (Italy). Part of ESRO.
ESRO European Space Research Organization.
essential loads Those loads that must be served to keep plant operations at an acceptable level during a prolonged commercial power outage. Such loads might be interruptible for periods of a few seconds to several minutes.
ESTEC European Space Technology Centre (Hol land). Part of ESRO.
estuary A partially enclosed body of water in the lo wer reaches of a river which is freely connected with the sea and which receives fresh water supplies from upland drainage areas.
etalon, measurement standard A material measu re, measuring instrument or system intended to define, realize, conserve or reproduce a unit or one or more known values of a quantity in order to transmit them to other measuring instruments by comparsion. Ex amples: a. 1 kg mass standard; b. standard gage block; c. 100 ohm standard resistor; d. saturated Wes ton standard cell; e. standard ammeter; f. caesium atomic frequency standard.
etch cracks Shallow cracks in the surface of harde ned steel due to hydrogen embrittlement that someti mes occurs when the metal comes in contact with an acidic environment.
etched circuit Refers to integrated circuits and the particular construction in a geometric design or pa- thing arrangement to form active elements by an et ching process on a single piece of semiconducting material.
ethane 153 exchange ethane A simple hydrocarbon associated with petrole
um. Ethane is a gas at ordinary atmospheric condi tions.
ethanol Alcohol; one component of gasohol.
ethernet A coaxial cable network in which all stations monitor the cable (the ether) during their own trans- mission, ending transmission immediately if a collisi on is detected.
ETHERNET A baseband LAN developed by Xerox Corporation and supported by Intel, DEC, Hewlett- Packard and others. It uses a bus topology with CSMA/CD access control.
ethylene propylene rubber seal Copolymer of et hylene and propylene. Resistant to phosphate ester fluid but not to mineral oils.
ETSU Energy Technology Support Unit (UK).
Eu Chemical symbol for Europium.
eukaryotic Descriptive of organisms whose cells have a visible and definite nucleus.
Euler number The Euler number is the ratio of iner tia forces to the pressure forces affecting the flow stream. See further ISA handbook of control valves relating to hydrodynamic noise prediction.
euphotic zone The upper layer of a body of water where light penetration is sufficient to support effecti ve photosynthesis.
EUROCAI European Organisation for Civil Aviation Electronic Industries.
Euronet European packet switching network. Euro net is sponsored by the European Economic Commu nity.
EUROSPACE European Industrial Space Research Group.
EUT Equipment Under Test.
eutectic Material, predominantly one of regular structure, made up to one or more phases formed si multaneously during solidification; see eutectoid, pe ritectic, peritectoid. An eutectic has a definite compo sition and is formed from the liquid phase at a definite temperature, the so-called eutectic temperature (where two phases are concerned).
eutectic alloy An alloy with a low and sharp melting point which converts from a solid to a liquid state at a specified recurring point. Used in thermal overload devices.
eutectoid Material of such composition that at a cer tain temperature during cooling it is transformed from one solid phase to a mixture of two solid phases; see eutectic, peritectic, peritectoid. The best known eutec toid is undoubtedly pearlite, which consists of fine, al ternating layers of ferrite and cementite formed by the transformation of austenite.
eutrophication (water quality) The enrichment of water both fresh and saline, by nutrients, especially compounds of nitrogen and phosphorus, that will ac celerate the growth of algae and higher forms of plant life.
eV Electron volt.
evaluating Determination of characteristic values of relationships of a process from measured values of process variables.
evaluation standard A standard on the methods and procedures of how to obtain the functional and perfor mance characteristics of a specific type of equipment. No requirements are stated as to the values to be ob tained.
evaporated make-up Distilled water used to supp lement returned condensate for boiler feed water.
evaporation The change of state from a liquid to a vapor.
evaporation deposits Percentage to residue obtai ned after evaporation of the product in free air.
evaporation plant (for waste liquor) Pertaining to pulp and paper manufacturing, an installation in which water and other substances are driven off from the waste liquor by heating, so that the dry solids con- tent is increased.
evaporative cooling 1. Lowering the temperature of
a mass of liquid by evaporating part of it, using the la- tent heat of vaporization to dissipate a significant amount of heat. 2. Cooling ambient air by evaporating water into it. 3. See vaporization cooling.
evaporator Any of several devices where liquid un dergoes a change of state from liquid to gas under re latively low temperature and low pressure.
even parity check A parity check in which the num ber of zeros (or of ones) in a group of binary digits is expected to be even.
event The occurrence of some programmed action within a process which can affect another process.
event-driven Computer program or process where each step of the execution relies on external actions.
event flag In a computer, an easily implemented synchronization mechanism that can be used for pas- sing messages and data buffers between two coopera ting tasks.
event orientated Pertaining to a physical occurren ce.
event recorder A recording instrument which re- cords the presence or absence of a quantity or the state of a two-state device as a function of time.
event tree analysis, ETA A method of representing and evaluating the possible sequences of events follo wing from a failure in a part of a system.
EWICS European Workshop in Industrial Computer Systems, the European industrial computer control standards group.
EXACT International Exchange of Authenticated Electronic Component Performance Test Data.
excecutive mode A central processor mode charac terized by the lack of memory protection and reloca tion by the normal execution of all defined instruction codes.
exception An event that causes suspension of normal program execution.
exception In a computer, a condition which is out of the ordinary in normal task execution; e.g., arithmetic overflow.
exception reporting An information system which reports on situations only when actual results differ from planned results. When results occur within a normal range they are not reported.
excess air Air supplied for combustion in excess of that theoretically required for complete oxidation.
excess fifty In a computer, a representation in which a number N is denoted by the equivalent of (N plus 50).
excess insertion loss (fiber optics) In an optical waveguide coupler, the optical loss associated with that portion of the light which does not emerge from the nominally operational ports of the device.
excess sound pressure The total instantaneous pressure at a point in a medium containing sound wa ves, minus the static pressure when no sound waves are present. The unit is the dyne per square centimeter.
excess three code The binary-coded decimal nota tion in which a decimal digit n is represented by the binary numeral that represents (n+3).
exchange To remove the contents of one storage unit of a computer and place it in a second, at the same
exchange network 154 experimental model
time placing the contents of the second storage unit into the first.
exchange network The public switched telephone system. Often referred to as the message network, the toll system, or the telephone network.
exchange register See memory register.
excitability (electrobiology) The inherent ability of a tissue to start its specific reaction in response to an electric current.