1、ISA THE INSTRUMENTATION, SYSTEMS AND AUTOMATION SOCIETY ELECTRONIC MEDIA PUBLICATIONS INDIVIDUAL LICENSE AGREEMENT ISA grants only a license to this copyrighted material. You may access the ISA publications under this license as long as you comply with the license terms and conditions set forth belo
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9、 publication or a refund of the license fee paid. ISA will not be liable to you for any special, incidental, consequential, or exemplary damages, including damages for lost time, lost profits, and computer problems, even if ISA has been informed of the possibility of such damages. In no case will IS
10、As liability exceed three times the license fee paid, even if the exclusive remedy is deemed inadequate. General Copyright 2003 by ISA The Instrumentation, Systems, and Automation Society All Rights Reserved. Produced in the United States of America. ISBN: 1-55617-941-3 This license will be governed
11、 by the laws of the State of North Carolina as if wholly performed and executed in that state. This is the entire agreement of the parties and supersedes all prior communications between the parties. This license may not be modified except in writing signed by an authorized representative of ISA. Yo
12、u acknowledge that you have read this license, understand it, and agree to be bound by it. All questions regarding this ISA product should be sent to: ISA The Instrumentation, Systems, and Automation Society PO Box 12277 Research Triangle Park, North Carolina 27709 http:/www.isa.org 3AB (alpha) Aver
13、age percent-age change in resistance per degree of pure metal resis-tance of device between 0C and 100C. Usually desig-nated by the Greek letter alpha, with units of W/W/C.aberration Deviation from ideal behavior by a lens, optical system, or optical component. Aberration exists in all optical syste
14、ms, and designers must make trade-offs among the different types depending on how much aberration they will tolerate.ABI Application Binary Interface; to run without porting.abnormally distributed uncertainty In the ISA recommended practice ISA-RP67.04.02-2000 this term denotes uncertainties that do
15、 not have a normal distribution. abort In data processing, to terminate a com-puter operation before its normal conclusion.abrasion 1. The act of removing surface mate-rial from a substance through sliding or roll-ing contact with the hard particles made of the same or another substance. The particl
16、es themselves may be loose or part of another surface brought into contact with the first. 2. A surface blemish caused by roughening or scratching.abrasive 1. Particulate matter, usually having sharp edges or points, that can be used to shape and finish workpieces in grinding, honing, lapping, polis
17、hing, blasting, or tum-bling processes. Depending on the process, abrasives may be loose, formed into solid shapes, glued to paper or cloth, or sus-pended in a paste, slurry, or air stream. 2. Any substance capable of removing material from a surface through the act of abrasion. 3. A material formed
18、 into a solid mass, usually fired or sintered, and used to grind or polish workpieces; common forms are grinding wheels, abrasive disks, honing sticks, cones, and burrs.ABS Acrylonitrile butadiene styrene; fre-quently used for enclosures; good high-tem-perature resistance with high impact strength a
19、nd cold-temperature impact, good overall chemical resistance; can be adversely affected by ultraviolet.absolute accuracy error The deviation of the analog value at any code from its theoretical value after the full-scale range has been cali-brated. Expressed in percent, ppm, or frac-tions of 1 LSB.a
20、bsolute address An address that indicates the exact storage location at which the refer-enced operand is to be found or stored in the actual machine code address numbering sys-tem. It is synonymous with specific address and actual address and related to absolute code.absolute alarm An alarm caused w
21、hen a sys-tem has detected a variable that has exceed-ed a set of prescribed high- or low-limit con-ditions.absolute altimeter See terrain clearance indica-tor.absolute altitude Distance between an air-craft or spacecraft and the actual surface of a planet or natural satellite.absolute code Coding t
22、hat uses machine instructions with absolute addresses. Synon-ymous with specific code.absolute encoder An electronic or electrome-chanical device that produces a unique digi-tal output (in coded form) for each value of an analog or digital input. In an absolute rotary encoder, for instance, you can
23、deter-mine directly the position following any incremental movement, without having to refer to the starting position.absolute feedback In numerical control, the action of assigning a unique value to each possible position of a machine slide or actu-ating member.absolute humidity The weight of water
24、 vapor in a gaswater vapor mixture per unit volume of space occupied, as, for example, grains or pounds per cubic foot.absolute instrument An instrument that determines the value of a measured quantity in absolute units by making a simple physi-cal measurement.absolute measurement A measured value t
25、hat is expressed in terms of fundamental standards of distance, mass, and time.absolute pressure 1. The pressure measured relative to zero pressure (vacuum). 2. The combined local pressure that is induced by some source and the atmospheric pressure at the location of the measurement. 3. Gauge pressu
26、re plus barometric pressure expressed in the same units of measurement.absolute programming In numerical control, the process of using a single point of refer-ence to determine all positions and dimen-sions.absolute stability A linear system is abso-lutely stable if there exists a limiting value of
27、the open-loop gain such that the system is stable for all lower values of that gain and unstable for all higher values.absolute value error The magnitude of the error disregarding the algebraic sign or, if a vectorial error, disregarding its direction.Aabsolute viscosity / accelerometer4ABabsolute v
28、iscosity A measure of the internal shear properties of fluids. It is expressed as the tangential force per unit area at either of two horizontal planes separated by one unit thickness of a given fluid, with one of the planes fixed and the other moving with unit velocity.absorbance An optical propert
29、y expressed as log (1/T), where T is the transmittance.absorptance The fraction of the incident light absorbed by something. absorption Sci 1. The reduction in intensity of a beam of electromagnetic or particulate radiation as it passes through matter. This reduction is chiefly due to interactions w
30、ith atoms or electrons or with their electric and magnetic fields. Comm 2. In fiber-optic cable, the loss of power resulting from the conversion of optical energy into heat. This loss is usually caused by impurities such as transition metals and hydroxyl ions.absorption band A region of the electrom
31、ag-netic spectrum in which a given substance exhibits a high absorption coefficient com-pared to adjacent regions of the spectrum.absorption coefficient An inherent material property that is expressed as the fractional loss in radiation intensity per unit mass or per unit thickness. It is determined
32、 over an infinitesimal thickness of the given material at a fixed wavelength and bandwidth.absorption curve A graph showing the varia-tion of transmitted radiation through a fixed sample while the wavelength material of a given thickness is changed at a uniform rate.absorption dynamometer A device f
33、or mea-suring mechanical force or power by con-verting the mechanical energy into heat in a friction mechanism or bank of electrical resis-tors.absorptionemission pyrometer An instru-ment for determining gas temperature by measuring the radiation emitted by a cali-brated reference source both before
34、 and after the radiation passes through the gas, where it is partly absorbed.absorption hygrometer An instrument for determining the water vapor content of the atmosphere by measuring the amount of water absorbed by a hygroscopic chemical.absorption meter An instrument for measur-ing the quantity of
35、 light transmitted through a transparent medium by means of a photo-cell or other light-detecting device.absorption spectroscopy The study of the wavelengths of light that are absorbed by materials and the relative intensities at which different wavelengths are absorbed. This technique can be used t
36、o identify materials and measure their optical densities.AC Alternating current; electric current that reverses its direction at regularly recurring intervals, such as 60 times/second (60 Hz).accelerated life test A method for estimating the reliability or durability of a product by subjecting it to
37、 operating conditions above its maximum ratings.accelerating agent 1. A substance that increa-ses a chemical reaction rate. 2. A chemical that hastens the curing of rubber, plastic, cement or adhesives, and may also improve their properties. Also known as accelerator.accelerating electrode An auxili
38、ary electrode in an electron tube that is maintained at an applied potential so as to accelerate electrons in a beam.acceleration The time rate of change of veloc-ity; the second derivative of a distance func-tion with respect to time.acceleration error The maximum difference, at any measured value
39、within the specified range, between output readings taken with and without the application of specified con-stant acceleration along specified axes. Note: See transverse sensitivity when applied in the context of acceleration transducer.acceleration limit The maximum vibration and shock acceleration
40、 that the transducer can accept in either direction along its sensi-tive axis without permanent damage. This limit is usually stated as + _gs. The acceleration limits are usually much wider than the acceleration range and thereby rep-resent a measure of the overload capability of the transducer. ISA
41、/RP-37.2 (R1995) acceleration range The range of accelerations over which the transducer has the specified linearity. ISA/RP-37.2 (R1995) acceleration time Comp 1. The amount of time it takes a mechanical component of a computer to go from rest to running speed. Sci 2. The measurement of the time re
42、quired for any object to reach a predeter-mined speed.accelerators A feature of some computer applications to create keyboard commands that provide alternatives to screen menus for selecting choices. The keystroke has special meaning within that particular application, which means more involved, but
43、 usually more “user- friendly,” procedures can be saved for making requests or entries.accelerometer 1. An instrument for measur-ing acceleration or an accelerating force such as gravity. If the instrument includes provi-sions for making a recorded output, it is acceptance angle / accumulator5ABcall
44、ed an “accelerograph.” 2. A transducer used to measure linear or angular accelera-tion.acceptance angle In fiber-optic cable, the half angle of cone within which incident light is totally reflected internally by the fiber core.acceptance test A series of tests used to demonstrate the capabilities an
45、d workability of a new system and usually conducted by the manufacturer to show the customer that the system is in working order.access The state in which it is permissible to place information into, or retrieve informa-tion, from a storage device.access, direct storage (DSA) The procedure whereby d
46、ata are transferred to or from stor-age that is essentially coincident with the normal operation of a computer, without dis-turbing the central processing unit registers. ISA/RP-55.1-1975 (R1983) access, random 1. The process of obtaining data from, or placing data into, storage such that the time r
47、equired for such access is inde-pendent of the location of the data most recently obtained or stored. 2. A type of stor-age device in which the access time is effec-tively independent of the location of the data. ISA/RP-55.1-1975 (R1983) access, serial The process of obtaining data from, or placing
48、data into, storage when there is a sequential relation governing the time it takes to access successive storage locations. ISA/RP-55.1-1975 (R1983) access code A group of alphanumeric charac-ters that identifies the user to the system so information can be placed or retrieved by other devices in the
49、 system.access line The portion of a leased communi-cation line, such as in a telephone system, that permanently connects the user with the serving central office or wire center.access method Any of the data-management techniques available to the user for transfer-ring data between main storage and an input/output device.access privilege The right or permission to access (read or write) a file that is granted by the processor after such permission has been requested. access procedures The procedure by which the devices attached to the netwo
