BS EN 60746-2-2003 Expression of performance of electrochemical analyzers - pH value《电化学分析仪性能的表示法 pH值》.pdf

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1、BRITISH STANDARD BS EN 60746-2:2003 Incorporating Corrigendum No. 1 Expression of performance of electrochemical analyzers Part 2: pH value The European Standard EN 60746-2:2003 has the status of a British Standard ICS 71.040; 19.040 BS EN 60746-2:2003 This British Standard was published under the a

2、uthority of the Standards Policy and Strategy Committee on 19 June 2003 BSI 5 September 2003 ISBN 0 580 42057 4 National foreword This British Standard is the official English language version of EN 60746-2:2003. It is identical with IEC 60746-2:2003, including Corrigendum July 2003. It supersedes B

3、S 6438-2:1984 which is withdrawn. This Part 2 of EN 60746 should be used in conjunction with EN 60746-1. The UK participation in its preparation was entrusted by Technical Committee GEL/65, Industrial Process measurement and control, to Subcommittee GEL/65/4, Process instruments for gas and liquid a

4、nalysis, which has the responsibility to: A list of organizations represented on this subcommittee can be obtained on request to its secretary. Cross-references The British Standards which implement international or European publications referred to in this document may be found in the BSI Catalogue

5、 under the section entitled “International Standards Correspondence Index”, or by using the “Search” facility of the BSI Electronic Catalogue or of British Standards Online. This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct

6、 application. Compliance with a British Standard does not of itself confer immunity from legal obligations. aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests inform

7、ed; monitor related international and European developments and promulgate them in the UK. Summary of pages This document comprises a front cover, an inside front cover, the EN title page, pages 2 to 21 and a back cover. The BSI copyright notice displayed in this document indicates when the document

8、 was last issued. Amendments issued since publication Amd. No. Date Comments 14565 Corrigendum No. 1 5 September 2003 Revision of Table B.2EUROPEAN STANDARD EN 60746-2 NORME EUROPENNE EUROPISCHE NORM February 2003 CENELEC European Committee for Electrotechnical Standardization Comit Europen de Norma

9、lisation Electrotechnique Europisches Komitee fr Elektrotechnische Normung Central Secretariat: rue de Stassart 35, B - 1050 Brussels 2003 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members. Ref. No. EN 60746-2:2003 E ICS 71.040; 19.040 Incorpora

10、ting Corrigendum No. 1 English version Expression of performance of electrochemical analyzers Part 2: pH value (IEC 60746-2:2003) Expression des qualits de fonctionnement des analyseurs lectrochimiques Partie 2: Mesure du pH (CEI 60746-2:2003) Angabe zum Betriebsverhalten von elektrochemischen Analy

11、satoren Teil 2: pH-Wert (IEC 60746-2:2003) This European Standard was approved by CENELEC on 2003-02-01. CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any altera

12、tion. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CENELEC member. This European Standard exists in three official versions (English, French, German). A version in any other language made by tra

13、nslation under the responsibility of a CENELEC member into its own language and notified to the Central Secretariat has the same status as the official versions. CENELEC members are the national electrotechnical committees of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greec

14、e, Hungary, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Slovakia, Spain, Sweden, Switzerland and United Kingdom.EN 60746-2:2003 - 2 - Foreword The text of document 65D/90A/FDIS, future edition 2 of IEC 60746-2, prepared by SC 65D, Analysing equipment, of IEC TC 65, Ind

15、ustrial-process measurement and control, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as EN 60746-2 on 2003-02-01. This Part 2 of EN 60746 shall be used in conjunction with EN 60746-1. The following dates were fixed: latest date by which the EN has to be implemented at

16、national level by publication of an identical national standard or by endorsement (dop) 2003-11-01 latest date by which the national standards conflicting with the EN have to be withdrawn (dow) 2006-02-01 Annexes designated “normative“ are part of the body of the standard. Annexes designated “inform

17、ative“ are given for information only. In this standard, annexes C and ZA are normative and annexes A and B are informative. Annex ZA has been added by CENELEC. _ Endorsement notice The text of the International Standard IEC 60746-2:2003 was approved by CENELEC as a European Standard without any mod

18、ification. _ Page2 EN607462:2003 CONTENTS 1 Scope.5 2 Normative reference.5 3 Definitions 5 4 Procedure for specification .8 4.1 Additional statements on sensor units and analyzers.8 4.2 Additional statements on electronic units.8 4.3 Statements on sensors9 4.3.1 General.9 4.3.2 Reference electrodes

19、9 4.3.3 pH sensor9 4.3.4 Temperature compensator.9 4.3.5 Auxiliary devices for sensor unit 9 5 Recommended standard values and ranges of influence quantities affecting the performance of electronic units.10 6 Verification of values10 6.1 General aspects10 6.2 Test procedures for electronic units.10

20、6.2.1 pH scaling.10 6.2.2 Isopotential pH, pH i .11 6.2.3 Temperature compensation.11 6.3 Test procedures for sensor units .11 6.3.1 Zero point pH 11 6.3.2 Percentage theoretical slope.11 6.3.3 Isopotential pH , pH i .11 6.4 Test procedures for analyzers .11 6.4.1 Intrinsic uncertainty.12 6.4.2 Line

21、arity uncertainty12 6.4.3 Repeatability.12 6.4.4 Output fluctuation12 6.4.5 Warm-up time12 6.4.6 Drift.12 6.4.7 Response times.12 6.4.8 Sample temperature12 6.4.9 Primary influence quantities.12 Bibliography21 Annex A (informative) .14 Annex B (informative) Reference buffer solutions: pH as a functi

22、on of temperature15 Annex C (normative) Alternative procedures for measuring response times: delay (T 10 ), rise (fall) (T r , T f ) and 90% (T 90 ) times.18 Page3 EN607462:2003 Annex ZA (normative) Normative references to international publications with their corresponding European publications .20

23、 Figure C.1 Relation between T 10 , T r(T f ) and T 90 . .18 Table A.1 Values of the slope factor, k = 2,3026 R.T/F 14 Table B.1 Values of reference pH buffer solutions at various temperatures16 Table B.2 Composition of reference pH buffer solutions.17 Page4 EN607462:2003 EXPRESSION OF PERFORMANCE O

24、F ELECTROCHEMICAL ANALYZERS Part 2: pH value 1 Scope This International Standard is intended: to specify terminology, definitions and requirements for statements by manufacturers for analyzers, sensor units and electronic units used for the determination of the pH of aqueous solutions; to establish

25、performance tests for such analyzers, sensor units and electronic units; to provide basic documents to support the applications of quality assurance standards ISO 9001, ISO 9002 and ISO 9003. 2 Normative reference The following referenced documents are indispensable for the application of this docum

26、ent. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. IEC 60746-1:2002, Expression of performance of electrochemical analyzers Part 1: General ISO 9001, Quality management systems Requireme

27、nts ISO 9002, Quality systems Model for quality assurance in production, installation and servicing ISO 9003, Quality systems Model for quality assurance in final inspection and test 3 Terms, definitions, symbols and abbreviations 3.1 Terms and definitions For the purposes of this part of IEC 60746,

28、 the definitions given in Clause 3 of IEC 60746-1, as well as the following apply. 3.1.1 pH value A measure of the conventional hydrogen ion activity a H+ (see equation (1), in an aqueous solution given by the expression: pH = log a H+It is measured with respect to pH values assigned to certain refe

29、rence pH buffer solutions. The measurement is performed by determining the e.m.f., E, between a pair of electrodes immersed in the sample to be measured, according to the cell scheme: Page5 EN607462:2003 Reference electrode I Sample I pH electrode E and a measurement with the same electrode pair at

30、the same temperature in a reference buffer solution of pH (S 1 ) according to Reference electrode I Buffer (S 1 ) I pH electrode E(S 1 ) The e.m.f.s E(S 1 ), etc. are defined as the difference of the potential of the right-hand (pH) electrode minus the potential of the left-hand (reference) electrod

31、e. The pH of the sample is then given ideally by: k E E ) S ( ) pH(S pH 1 1 = (1) where k = 2,3026 R.T/F, the theoretical, Nernstian, slope (see 3.1.2) . Numerical values for k, the theoretical slope factor, at temperatures from 0 C to 95 C, are given in Annex A. NOTE Measurements in non or partiall

32、y aqueous media are beyond the scope of this document; the reader should refer to specialist texts. 3.1.2 practical slope factor and percentage theoretical slope PTS performance of the electrode pair may fall below the theoretical slope k exhibiting the practical slope k which may be determined by r

33、eplacing the sample with a second reference buffer solution of pH value pH (S 2 ) with an e.m.f. E(S 2 ), then: ( ) ( ) () () 2 1 1 2 S pH S pH S S = E E k (2) NOTE The difference in pH value between the two reference buffer solutions should be as large as possible, however, solutions above pH 10 an

34、d below pH 3 should not generally be used (see Annex B). The percentage theoretical slope (PTS) is given by: k k PTS = 100Equations (1) and (2) can be combined by substituting k for k in equation (1) where: () ( ) ( ) ( ) ()() 1 2 2 1 1 1 S S S pH S pH S S pH H E E E E p = (3) and the two reference

35、buffers are usually chosen to bracket the pH of the sample. 3.1.3 pH sensor the most commonly used pH sensor is the glass electrode, other potentiometric sensors, for example, the antimony electrode only being adopted when its use is precluded. The pH isfet (ion selective field effect transistor) se

36、nsor is an alternative to potentiometric sensors, necessitating manufacturer-specific instrumentation. Page6 EN607462:2003 3.1.4 reference electrode appropriate half-cell providing a stable potential at constant temperature against which the potential of the pH sensor is measured. Electrical contact

37、 with the sample is made at a liquid- junction with the reference electrolyte or an interposed bridge solution. 3.1.5 temperature compensator electrical sensor in thermal contact with the sample providing the means for temperature compensation 3.1.6 sensor unit insertion or flow-through housing into

38、 which pH and reference sensors, as well as usually, a temperature compensator (see 4.3.4) and possibly auxiliary devices (see 4.3.5) are fitted. 3.1.7 zero point pH pH value at which the e.m.f. of the electrode pair (sensor unit) is 0 V at a given temperature, unless otherwise stated, understood to

39、 be 25 C. 3.1.8 isopotential pH, pH i , of the electrode pair (sensor unit) pH, pH i , at which the e.m.f., E i , of the electrode pair is temperature invariant. It is a function of the temperature coefficients of the individual electrodes and provides temperature compensation for the electrode pair

40、 zero shift with appropriate instrumentation. 3.1.9 alkaline (or sodium) error of the glass electrode error of the e.m.f. caused by sensitivity of pH glass electrodes to alkali ions at high pH resulting in apparent low pH values. Major interferences are Na + Li + K + Ba 2+. Errors increase with incr

41、easing alkali concentration, pH and temperature. The magnitude is dependent on the glass membrane composition. 3.1.10 reference buffer solution aqueous solution prepared according to a specific formula using recognized analytical grade chemicals and water having a conductivity no greater than 2 Scm

42、1 at 25 C(see Annex B) 3.1.11 solution ground (earth) electrode inert metal electrode required for differential input instrumentation as a comparison point against which glass and reference electrode potentials are determined. For other applications, it establishes the sample potential at instrument

43、 ground (earth) 3.1.12 simulator simulator providing Nernstian values of e.m.f.s (see 3.1.1 and Table A.1), representing pH values at selected temperatures through a high value series resistor representative of pH sensors. The simulator comprises a stepped voltage source followed by a selectable ser

44、ies resistor. The network is such that output voltage steps represent multiples, and may provide sub- multiples, of e.m.f. representing unit pH steps for selectable temperatures. The resistance of the voltage divider network should not exceed 10 k and the selectable series resistor should be 1 000M

45、(10%). Page7 EN607462:2003 3.2 Symbols a H+= hydrogen ion activity pH = pH of the solution measured at temperature t pH(S 1 ) = pH of the first reference buffer solution at temperature t pH(S 2 ) = pH of the second reference buffer solution at temperature t pH i= pH at the isopotential point E = e.m

46、.f. in the measured sample at temperature t E(S 1 ) = e.m.f. in the first reference buffer solution at temperature t E(S 2 ) = e.m.f. in the second reference buffer solution at temperature t E i= e.m.f. at the isopotential point F = the Faraday constant R = the molar gas constant t = temperature in

47、degrees celsius T = the temperature in kelvin of sample k = the theoretical, Nernstian, slope of the electrode pair at temperature t k /= the practical slope of the electrode pair at temperature t 4 Procedure for specification See Clause 5 of IEC 60746-1, plus the following: NOTE Uncertainties and u

48、ncertainty limits should be stated in pH values. 4.1 Additional statements on sensor units and analyzers 4.1.1 Type of sensor unit (i.e., flow-through or insertion unit). 4.1.2 Sensor unit dimensions, including mounting and connections. 4.2 Additional statements on electronic units 4.2.1 Number of d

49、igits and size of display, or for analogue instruments, scale width. 4.2.2 Output signal/signals, if adjustable, whether isolated from input and/or ground (earth) and permitted output load. 4.2.3 Temperature compensation range, compensator type and maximum permitted resistance of compensator plus connection cable; if only manual compensation available, it shoul