BS ISO 24115-2012 Green coffee Procedure for calibration of moisture meters Routine method《生咖啡 湿度计校准规程 常规方法》.pdf

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1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS ISO 24115:2012Green coffee Procedure forcalibration of moisture meters Routine methodBS ISO 24115:2012 BRITISH STANDARDNational forewordThis British Standard is the UK impleme

2、ntation of ISO 24115:2012.The UK participation in its preparation was entrusted to TechnicalCommittee AW/15, Coffee.A list of organizations represented on this committee can beobtained on request to its secretary.This publication does not purport to include all the necessaryprovisions of a contract.

3、 Users are responsible for its correctapplication. The British Standards Institution 2012. Published by BSI StandardsLimited 2012ISBN 978 0 580 66463 2ICS 67.140.20Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was published under the authority

4、of theStandards Policy and Strategy Committee on 30 June 2012.Amendments issued since publicationDate T e x t a f f e c t e dBS ISO 24115:2012 ISO 2012Green coffee Procedure for calibration of moisture meters Routine methodCaf vert Mode opratoire dtalonnage des humidimtres Mthode de routineINTERNATI

5、ONAL STANDARDISO24115First edition2012-06-01Reference numberISO 24115:2012(E)BS ISO 24115:2012ISO 24115:2012(E)ii ISO 2012 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2012All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or

6、 by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISOs member body in the country of the requester.ISO copyright officeCase postale 56 CH-1211 Geneva 20Tel. + 41 22 749 01 11Fax + 41 22 749 09 47E-mail

7、 copyrightiso.orgWeb www.iso.orgPublished in SwitzerlandBS ISO 24115:2012ISO 24115:2012(E) ISO 2012 All rights reserved iiiContents PageForeword iv1 Scope 12 Normative references . 13 Terms and definitions . 14 Principle . 15 Equipment and material . 16 Procedure 26.1 Test conditions . 26.2 Alignmen

8、t of instrument deviation . 26.3 Calibration of moisture meter 26.4 Temperature correction . 36.5 Calculation of uncertainty . 46.6 Calibration curves for indirect reading equipment 57 Expression of results . 5Annex A (normative) Reference sample preparation and determination of moisture content as

9、a mass fraction loss 6Annex B (informative) Example for moisture determination of samples to serve as reference . 9Annex C (informative) Results of interlaboratory tests 11Annex D (informative) Examples for separate steps of the procedure 12Bibliography .16BS ISO 24115:2012ISO 24115:2012(E)ForewordI

10、SO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical c

11、ommittee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electr

12、otechnical standardization.International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the mem

13、ber bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote.Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifyi

14、ng any or all such patent rights.ISO 24115 was prepared by Technical Committee ISO/TC 34, Food products, Subcommittee SC 15, Coffee.iv ISO 2012 All rights reservedBS ISO 24115:2012INTERNATIONAL STANDARD ISO 24115:2012(E)Green coffee Procedure for calibration of moisture meters Routine method1 ScopeT

15、his International Standard specifies a procedure for adjustment and subsequent calibration of moisture meters for green coffee beans with reference samples (RSs).The RSs are green coffee beans of various moisture contents, determined by a standard method (ISO 6673).NOTE This method of determining th

16、e loss in mass can be considered, by convention, as a method for determining the water content and can be used as such by agreement between the interested parties.This International Standard is applicable to green coffee as beans.2 Normative referencesThe following referenced documents are indispens

17、able for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.ISO 3509, Coffee and coffee products VocabularyISO 6673:2003, Green coffee Determination of loss i

18、n mass at 105 CISO/IEC Guide 99, International vocabulary of metrology Basic and general concepts and associated terms (VIM)3 Terms and definitionsFor the purposes of this document, the terms and definitions given in ISO 3509, ISO/IEC Guide 99, and the following apply.3.1reference sampleRSsample of

19、green coffee beans, sufficiently homogeneous and stable with reference to specified properties, which has been established to be fit for its intended use in measurement or in examination of nominal propertiesNOTE See Annex A.4 PrincipleFrom green coffee beans, a set of samples with different moistur

20、e contents is prepared, to be taken as reference samples (RS). Their individual moisture content (or mass fraction loss) values are obtained by the respective determinations of loss in mass by applying ISO 6673.These RSs with assigned moisture values are used for calibration of moisture meters.5 Equ

21、ipment and material5.1 Green coffee as beans, in a quantity sufficient to prepare n reference samples, RSi, i = 1 n (the minimum is 5), with moisture mass fraction ranges between 8,5 % and 13,5 %, prepared according to A.1. ISO 2012 All rights reserved 1BS ISO 24115:2012ISO 24115:2012(E)5.2 Thermome

22、ter, range between 0 C to 120 C, scale division 0,1 C, provided the moisture meter does not display the sample temperature.5.3 Moisture meter, equipped with all the accessories specified by the manufacturer. It shall include a channel for green coffee, which will be the subject of calibration.5.4 Ba

23、lance, capable of being read to the nearest 0,1 g.5.5 Equipment necessary for determinations according to ISO 6673.6 Procedure6.1 Test conditionsThe procedure shall be carried out at ambient temperature and at a relative humidity from 40 % to 70 %.Prior to the test, allow conditioning of the green c

24、offee bean RSs to ambient temperature.6.2 Alignment of instrument deviation6.2.1 Before adjustment, verify the equipment in accordance with the manufacturers instructions.NOTE The verification is necessary to ensure the electronic gauging.6.2.2 For moisture meters with direct reading, select green c

25、offee beans channel.6.2.3 For each RSi, obtain the difference between the reference sample moisture mass fraction, wRSi, determined according to ISO 6673, and the moisture meter reading, wri, where i is the reference sample number assigned. Record them as wi= wRSi- wriin the column headed “Differenc

26、e” of Table 1.6.2.4 Calculate the average of the differences, w , and adjust the moisture meter bias according to the manufacturers operation manual.Table 1 Input values to obtain the bias for moisture meter adjustmentReference sampleMoisture mass fraction of reference sampleaEquipment reading on sa

27、mpleDifferenceRSi, i = 1 n wRSiwriwi= wRSi- wriRS1 RS2 . RS(n - 1) RSn waThe moisture content (or mass fraction loss), wRSi, is obtained using ISO 6673.6.3 Calibration of moisture meter6.3.1 For calibration, use the moisture meter after adjustment (6.2).2 ISO 2012 All rights reservedBS ISO 24115:201

28、2ISO 24115:2012(E)6.3.2 Take the oven moisture values of the RSs, obtained according to A.2, and insert the figures into the appropriate wRSicells in Table 2.6.3.3 Take a test portion from RS1 in accordance with the equipment manufacturers instructions or the equipment capacity, and pour it into the

29、 moisture meter. Record the reading from the equipment in the cell matching the first row, RS1, and column, wri,1, of Table 2; this cell corresponds to wr1,1.Provided the equipment requires a defined test portion quantity, use the balance specified in 5.4.6.3.4 Repeat the the procedure specified in

30、6.3.3 with the same test portion twice and record the readings in the subsequent cells which correspond to wr1,2, and wr1,3for RS1.At least three determinations shall be performed.6.3.5 Calculate the arithmetic average of the RS1 readings, wr1,1, wr1,2, and wr1,3, and record it in the corresponding

31、cell of column wijr, i = 1 n; j = 1,2,3 of Table 2.6.3.6 Calculate the experimental standard deviation, s1, of wr1,1, wr1,2, and wr1,3and insert it into the corresponding cell of column siof Table 2.6.3.7 Measure the temperature of the test portion RS1 and record it in the corresponding cell of colu

32、mn Tiof Table 2.6.3.8 Repeat the procedure as specified in 6.3.3 to 6.3.7 with the other reference samples, RS2 to RSn and their test portions.6.3.9 Determine a correction term, Cri, to compensate for an estimated systematic effect of moisture for each wrimoisture reading by applying Formula (1)Cw w

33、iiijrRSr= i = 1 n j = 1,2,3 (1)NOTE For an example, see Table D.2.Table 2 Input values to obtain the calibration of moisture meterReference sampleSample temperature CEquipment readings on RSs and corresponding meanStandard deviation of readingReference sample moistureaMoisture meter correctionRSi Ti

34、wri,1wri,2wri,3wijr ,siwRSiCiwiwijr RS r=RS1 RS2 . RS(n - 1) RSn aThe moisture content (or mass fraction loss), wRSi, is obtained using ISO 6673; see A.2.6.4 Temperature correction6.4.1 Calculate the moisture reading correction term, CT, due to bean temperature (if not automatically done by the inst

35、rument itself) based on equipment manufacturer instructions; otherwise follow steps 6.4.2 to 6.4.5. ISO 2012 All rights reserved 3BS ISO 24115:2012ISO 24115:2012(E)NOTE Some manufacturers provide an automatic temperature correction programme with their instruments.6.4.2 Determine the moisture conten

36、t of the RSs with the moisture meter at a given temperature.6.4.3 Increase the temperature of the samples by about 5 C to 10 C and determine the new values at the moisture meter.6.4.4 For each RS, take the difference in moisture readings at test temperatures, and the difference of temperatures, and

37、calculate the respective ratioiiwT=r(2)6.4.5 Calculate the arithmetic mean of the ratios, , to obtain the resulting moisture reading correction term CTdue to bean temperature.CTTT=()refs(3)NOTE For an example, see Table D.4.6.5 Calculation of uncertaintyThis approach is based on that set out in ISO/

38、IEC Guide 98-3:2008.1When reporting the result of a measurement of a physical quantity, it is obligatory that some quantitative indication of the quality of the result be given so that those who use it can assess its reliability. Without such an indication, measurement results cannot be compared, ei

39、ther among themselves or with reference values given in a specification or standard.It is therefore necessary that there is a readily implemented, easily understood, and generally accepted procedure for characterizing the quality of a result of a measurement, that is, for evaluating and expressing i

40、ts uncertainty.1)The components of moisture measurement uncertainty are:a) URSi: uncertainty of the (assigned) value of the reference sample;b) sri/j: uncertainty type A given by the moisture meter readings obtained from the experimental standard deviation sriusing reference material i, with j = 3 r

41、epetitions (see 6.3.6);c) uBa: uncertainty type B due to moisture meter accuracy;d) uBr: uncertainty type B due to moisture meter resolution;e) uBTi: uncertainty type B due to the temperature (see 6.4 and D.4).Calculate the expanded uncertainty of the moisture meter, Umi, for each moisture point i u

42、sing Formula (4):UkUksuuuiiriTimRSBa Br B=+2 22223(4)where k is the coverage factor; generally k = 2 for a probability of 95 %, according to ISO/IEC Guide 98-3:2008.1For each individual case, it is necessary to check every possible source of uncertainty.1) In most cases, regressions are linear, howe

43、ver, it can prove necessary to apply another type, e.g. quadratic, regression.4 ISO 2012 All rights reservedBS ISO 24115:2012ISO 24115:2012(E)6.6 Calibration curves for indirect reading equipmentIf the equipment does not give a measurement result directly in moisture content, but as a dimensionless

44、value, generate a calibration curve by comparing the equipment readings for each sample with the moisture of the RSs.For a graphic calibration, plot the n values of the reading means, wijr, on the abscissa against the n values of sample moisture content, wiRSon the ordinate, with i = 1 . n for the s

45、amples and j = 1, 2, 3 for the replicate readings to obtain the calibration curve.The calibration curve relates the equipment readings to moisture content (or mass fraction loss) of the reference samples.For calculation, a linear regression is suitable in most cases.17 Expression of resultsThe moist

46、ure content of a sample, wHO2, determined using a moisture meter which has been calibrated with the method described in this International Standard, shall be expressed aswwCC UTHO rr m2=+() (5)wherewris the moisture content meter reading;Cris the correction for the moisture meter reading;CTis the co

47、rrection for the moisture meter due to the temperature;Umis the expanded uncertainty for the moisture mass fraction in the sample.All values are given as percentage mass fractions.NOTE D.6 gives an example of the final calculation. ISO 2012 All rights reserved 5BS ISO 24115:2012ISO 24115:2012(E)Anne

48、x A (normative) Reference sample preparation and determination of moisture content as a mass fraction lossA.1 Reference sample preparationA.1.1 Decide the number, n (n 5), of RSs to be used in the calibration process.A.1.2 Select the starting material, green coffee beans of single species and homoge

49、neous characteristics, with an initial moisture mass fraction between 14 % and 16 %.NOTE 1 Depending on the measurement principle of the moisture meter to be calibrated and the precision required, it can prove necessary to perform individual calibrations for coffees of different bulk or intrinsic characteristics of the beans, like shape, size or any steaming pretreatment used.NOTE 2 Some moisture meters allow different parallel installations o