1、Data Acquisition SystemsPerformance Test CodesAN AMERICAN NATIONAL STANDARDASME PTC 19.22-2007Revision of ANSI/ASME PTC 19.22-1986 (R1998)Intentionally left blank ASME PTC 19.22-2007Revision of ANSI/ASME PTC 19.22-1986 (R1998)Data AcquisitionSystemsPerformance Test CodesAN AMERICAN NATIONAL STANDARD
2、Date of Issuance: June 30, 2008This Code will be revised when the Society approves the issuance of a new edition. There will be noaddenda issued to ASME PTC 19.22-2007.ASME issues written replies to inquiries concerning interpretations of technical aspects of thisdocument. Periodically certain actio
3、ns of the ASME PTC 19.22 Committee may be published as CodeCases. Code Cases and interpretations are published on the ASME Web site under the CommitteePages at http:/cstools.asme.org as they are issued.ASME is the registered trademark of The American Society of Mechanical Engineers.This code or stan
4、dard was developed under procedures accredited as meeting the criteria for American NationalStandards. The Standards Committee that approved the code or standard was balanced to assure that individuals fromcompetent and concerned interests have had an opportunity to participate. The proposed code or
5、 standard was madeavailable for public review and comment that provides an opportunity for additional public input from industry, academia,regulatory agencies, and the public-at-large.ASME does not “approve,” “rate,” or “endorse” any item, construction, proprietary device, or activity.ASME does not
6、take any position with respect to the validity of any patent rights asserted in connection with anyitems mentioned in this document, and does not undertake to insure anyone utilizing a standard against liability forinfringement of any applicable letters patent, nor assumes any such liability. Users
7、of a code or standard are expresslyadvised that determination of the validity of any such patent rights, and the risk of infringement of such rights, isentirely their own responsibility.Participation by federal agency representative(s) or person(s) affiliated with industry is not to be interpreted a
8、sgovernment or industry endorsement of this code or standard.ASME accepts responsibility for only those interpretations of this document issued in accordance with the establishedASME procedures and policies, which precludes the issuance of interpretations by individuals.No part of this document may
9、be reproduced in any form,in an electronic retrieval system or otherwise,without the prior written permission of the publisher.The American Society of Mechanical EngineersThree Park Avenue, New York, NY 10016-5990Copyright 2008 byTHE AMERICAN SOCIETY OF MECHANICAL ENGINEERSAll rights reservedPrinted
10、 in U.S.A.CONTENTSNotice . vForeword viCommittee Roster . viiCorrespondence With the PTC 19.22 Committee viiiIntroduction . ixSection 1 Object and Scope . 11-1 Object . 11-2 Scope 1Section 2 Definitions and Descriptions of Terms 2Section 3 Guiding Principles. 43-1 Capability . 43-2 Typical Data Acqu
11、isition Systems 43-3 System Planning . 53-4 Operational Considerations 8Section 4 Signal Conversion . 94-1 Sensors 94-2 Signal Conditioning 94-3 Signal Multiplexing 12Section 5 Data Acquisition System Calibration 145-1 System Calibration . 145-2 Calibration Methods . 155-3 Field Calibration . 155-4
12、Laboratory Calibration . 15Section 6 System Uncertainty 166-1 System Uncertainty Contributors . 166-2 Overall System Uncertainty 18Section 7 Data Management. 197-1 Digital Data Representation 197-2 Data Output Requirements . 197-3 Manually Prepared Data . 207-4 Calculations . 207-5 Data Storage Guid
13、elines 247-6 Reporting 25Figures3-2-1 Basic Data Acquisition System Flowchart . 53-2-2 Intermediate Data Acquisition System Flowcharts . 63-2-3 Advanced Data Acquisition System Flowchart 77-4.1.3-1 Total Curve Fit . 217-4.1.3-2 Offset Curve Fit 227-4.1.3-3 Offset Straight Line Segments 23Mandatory A
14、ppendixI Bibliography . 27iiiNonmandatory AppendicesA Data Acquisition System Component Errors and Overall System UncertaintyRepresentation 28B Data Acquisition System Uncertainty Calculation Examples . 31C Floating-Point Data Representation (IEEE 754-1985) . 41D Sample Data Acquisition System Outpu
15、t Example 42ivNOTICEAll Performance Test Codes must adhere to the requirements of ASME PTC 1, GeneralInstructions. The following information is based on that document and is included here foremphasis and for the convenience of the user of the Supplement. It is expected that the Codeuser is fully cog
16、nizant of Sections 1 and 3 of ASME PTC 1 and has read them prior to applyingthis Supplement.ASME Performance Test Codes provide test procedures that yield results of the highest levelof accuracy consistent with the best engineering knowledge and practice currently available.They were developed by ba
17、lanced committees representing all concerned interests and specifyprocedures, instrumentation, equipment-operating requirements, calculation methods, and uncer-tainty analysis.When tests are run in accordance with a Code, the test results themselves, without adjustmentfor uncertainty, yield the best
18、 available indication of the actual performance of the tested equip-ment. ASME Performance Test Codes do not specify means to compare those results to contractualguarantees. Therefore, it is recommended that the parties to a commercial test agree before startingthe test and preferably before signing
19、 the contract on the method to be used for comparing thetest results to the contractual guarantees. It is beyond the scope of any Code to determine orinterpret how such comparisons shall be made.vFOREWORDThe scope of the Instruments and Apparatus Supplements (PTC 19 Series) is to describe thevarious
20、 types of instruments and methods of measurement likely to be prescribed in the ASMEPerformance Test Codes. Such details as the limits and sources of error, methods of calibration,precautions, etc., as will determine their range of application are usually given.PTC 19.22, Data Acquisition Systems, r
21、epresents an extension of the purpose of the Supplementsinto the realm of digital systems. These are increasingly becoming an integral part of moderntesting practice. In order that the ASME Performance Test Codes continue to provide test proce-dures characterized by the highest level of accuracy con
22、sistent with the best current engineeringpractice, it became necessary to develop and maintain a PTC document on this topic.Accordingly, on November 18, 1969, the Performance Test Codes Standing Committee (nowthe Performance Test Codes Standards Committee) authorized the organization of a TechnicalC
23、ommittee to develop a Supplement on instrumentation for computer information. However, atthat time it was difficult to obtain the services of qualified Committee personnel due to therelative novelty of applying digital systems to testing procedures. Nevertheless, a chairman wasappointed by November
24、1972 and a report on the object and scope was issued on November 20,1974. Regular Committee meetings began in 1976 and are held periodically.The previous edition, PTC 19.22-1986, Digital Systems Techniques, was adopted by the AmericanNational Standards Institute as an American National Standard on J
25、anuary 3, 1986.This revision, PTC 19.22-2007, Data Acquisition Systems, was approved by ASME CommitteePTC 19.22 on April 20, 2007. It was then approved by the American National Standards Institute(ANSI) as an American National Standard on September 12, 2007.viASME PTC COMMITTEEPerformance Test Codes
26、(The following is the roster of the Committee at the time of approval of this Standard.)STANDARDS COMMITTEE OFFICERSJ. G. Yost, ChairJ. R. Friedman, Vice ChairJ. H. Karian, SecretarySTANDARDS COMMITTEE PERSONNELP. G. Albert, General Electric Co.R. P. Allen, ConsultantR. L. Bannister, Member Emeritus
27、, ConsultantJ. M. Burns, Burns EngineeringW. C. Campbell, Southern Company ServicesM. J. Dooley, Alstom PowerA. J. Egli, Alstom PowerJ. R. Friedman, Siemens Power Generation, Inc.G. J. Gerber, ConsultantP. M. Gerhart, University of EvansvilleW. O. Hays, Honorary Member, RetiredT. C. Heil, The Babcoc
28、k however, theyshould not contain proprietary names or information.Requests that are not in this format will be rewritten in this format by the Committee priorto being answered, which may inadvertently change the intent of the original request.ASME procedures provide for reconsideration of any inter
29、pretation when or if additionalinformation that might affect an interpretation is available. Further, persons aggrieved by aninterpretation may appeal to the cognizant ASME Committee or Subcommittee. ASME does not“approve,” “certify,” “rate,” or “endorse” any item, construction, proprietary device,
30、or activity.Attending Committee Meetings. The PTC 19.22 Standards Committee regularly holds meetings,which are open to the public. Persons wishing to attend any meeting should contact the Secretaryof the PTC 19.22 Standards Committee.viiiINTRODUCTIONThe purpose of this Code is to define the scope an
31、dapplication of data acquisition systems for use withASME Performance Test Codes. The code is based onthe use of data acquisition systems covering a widerange of capability from simple data gathering equip-ment to multipurpose online or offline data acquisitionsystems.Use of this Code with any of th
32、e applications of ASMEPerformance Test Codes should include a review of thefollowing documents:(a) PTC 1ix(b) PTC 19.1(c) Appropriate ASME Performance Test Codes(d) Appropriate ASME Performance Test CodeReports and Guides(e) Appropriate Instruments and Apparatus Supple-mentsThe appropriate sections
33、of the Instruments andApparatus Supplements of the PTC 19 series and specifi-cally PTC 19.1, Measurement Uncertainty are essentialwhen selecting or developing data acquisition systems.Intentionally left blank ASME PTC 19.22-2007DATA ACQUISITION SYSTEMSSection 1Object and Scope1-1 OBJECTThe object of
34、 this Code is to provide guidance fordesign, selection, and application of the data acquisitionsystems used in ASME Code Performance Tests. ThisCode provides descriptions of the various data acquisi-tion system architectures and information on determin-ing system uncertainties and to assist in selec
35、ting andapplying these data acquisition systems. The Code isintended to address data acquisition systems used forASME Code Performance Testing but may also be usedfor guidance in selecting systems for any test applica-tion. These systems include systems specificallyinstalled for a test and plant Dis
36、tributed Control Systems(DCS) which also provide the ability to monitor sensorsduring a test. The Code is not intended to address longterm Performance Monitoring but may provide guid-ance for such applications.1-2 SCOPEThe scope of this Code includes signal conditioning,signal multiplexing, analog-t
37、o-digital signal conversion,1and data processing. This Code addresses stand-alonedata acquisition systems, typified by a sensor with anintegral digital display, data acquisition systems thatlink multiple sensors to a common digital processor tiedto a computer or printer, and systems that link multip
38、ledigital processors to one or more stand-alone or net-worked computers.This Code incorporates instrumentation practices cov-ered by other Instruments and Apparatus Supplements(PTC 19 Series) as well as by the equipment PerformanceTest Codes. It also provides a means to determine theuncertainty asso
39、ciated with the data acquisition system,and its impact on the overall uncertainty of the perform-ance test. The Code does not directly address specificsensors or instruments used for ASME PerformanceTesting. These are addressed in other ASMEPerformance Test Codes.ASME PTC 19.22-2007Section 2Definiti
40、ons and Descriptions of TermsThe following definitions are provided to clarify theterms used in this document:accuracy: the closeness of agreement between a measuredvalue and the true value 1.analog signal: a nominally continuous electrical signalthat varies in some direct correlation with another s
41、ignalimpressed on a transducer 2.analog-to-digital (A/D) converter: a device that convertsan analog signal to a digital signal that represents equiv-alent information 2.binary word: the maximum number of bits treated as aunit and capable of being stored in one location 3.bit: a contraction of the wo
42、rds “binary” and “digit” 3.calibration: the process of comparing the response of aninstrument to a reference standard over some measure-ment range.channel: a single path through a transmission mediaintended to carry the signal of an instrument reading.Typically, it carries the raw electrical signal
43、of the instru-ment, or the output of a multiplexing function.checksum bit (check bit): a bit, such as a parity bit, derivedfrom and appended to a bit string for later use in errordetection and possibly error correction 2.contact resistance: the resistance between the closed con-tacts of a relay in a
44、 multiplexer.crosstalk: the undesired signal appearing in one signalpath as a result of coupling from another signal path 3.dataacquisitionsystem: any device or collection of devicescapable of accepting information, converting this infor-mation to corresponding digital information, applyingprescribe
45、d processes to the information, and supplyingthe results of the processes 3.data compression: the method of filtering data, by excep-tion or other means, and storing it only if meeting speci-fied criteria. The primary function of this method is tooptimize data storage space by limiting the amount of
46、data being stored.data reduction: the method by which raw test data beingcollected by the data acquisition system is summarizedthrough simple calculations to produce more meaning-ful information.digital signal: data represented by discrete values or con-ditions 2.2double precision: use of two digita
47、l words together toincrease the resolution of a digital signal that could notbe represented by a single digital word.drift: a change in system output over time independentof the input signal.filtering: electric, electronic, acoustic, optical, or softwaredevices used to reject signals, vibrations, or
48、 radiationsof certain frequencies while allowing others to pass 2.full range (FR): the absolute value of the algebraic differ-ence between the minimum and maximum values forwhich the system is capable of measuring or generating.full scale: an instruments maximum reading or outputfor each of its rang
49、es 4. May have a higher numericvalue than the range setting due to overrange capability.gainerror(scaleerror): error in a signal due to nonlinearityin a devices response.least significant bit (LSB): right most bit in a binary wordwhose value contributes the least to the overall value ofthe binary word and also represents the resolution ofthe digital word.multiplexer: a device that combines two or more informa-tion channels onto a common transmission medium 2.noise: a disturbance that affects a signal and that maydistort the information carried by the signal 2
