Project: CООМЕТ 390/BY/07. SUPPLEMENTARY COMPARISON OF STANDARDS OF THE UNIT FOR LENGTH (METRE) IN THE MEASUREMENT RANGE FROM 0,1 TO 100 mm

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1 September 2011 Proect: CООМЕТ 390/BY/07 SUPPLEMENTARY COMPARISON OF STANDARDS OF THE UNIT FOR LENGTH (METRE) IN THE MEASUREMENT RANGE FROM 0,1 TO 100 mm COOMET.L-S7 DRAFT B REPORT Pilot laboratory: Belarusian State Institute of Metrology (BelGIM) Contact person: Mr. V. Makarevich BelGIM Geometrical quantities measurement section Starovilensky tract 93, Minsk, , Belarus, Fax Makarevich@belgim.by 1

2 1. Participants Table 1 No NMI Address NMI acronym 1 Belarussian State Institute of Metrology 2 Ukrmetrteststandart, Ukraine 3 Central Office of Measures, Poland 4 Slovak Institute of Metrology 5 National Scientific Center Institute of metrology 6 South Kazakhstan branch of RGP KazInMetr Starovilensky tract 93, Minsk, , Belarus Metrologicheskaya st. 4, Kiev, 03680, Ukraine ul. Elektoralna 2, Warszawa, Poland Karloveská 63, Bratislava 4, Slovakia Mironositskaya st. 42, Kharkov, 61002, Ukraine Orynbor st. 11, Levy bereg, Astana, , Kazakhstan BelGIM Ukrmetrteststandart GUM SMU NSCIM KazInMetr Contact person Vladimir Makarevich , phone, fax Tel: Fax: Makarevich@belgim.by Anna Fursa Tel: Fax: ukrcsm@ukrcsm.kiev.ua Zbignev Ramotovsky Ekaterina Kromkova Gennady Zimokosov Olga Isakova Tel: Fax: lenght@gum.gov.pl Tel: Fax: kromkova@smu.gov.sk Tel: ; Fax solovyov@metrology. kharkov.ua Tel: Fax: Olgai.52@mail.ru 2. Organization of comparison 2.1 Principle of comparison Scheme of comparison: mixed comparison Pilot laboratory: BelGIM The aim of comparison is to: - establish the degree of equivalence between the standards; - support the СМСs. 2.2 Time-schedule of comparison is described in Table 2. Table 2 NMI Measurement time Scheduled Actual BelGIM May 2007 May 2007 GUM May 2007 May 2007 Ukrmetrteststandart September 2007 November 2007 NCSIM December 2007 December 2007 SMU February 2008 June 2008 BelGIM (repeated measurements) June 2008 November 2009 KazInMetr - October

3 The measurements were performed on one quartz transfer standard and one steel transfer standard provided by BelGIM. 3 Transfer standards Picture 1- Quartz transfer standard Picture 2- Steel transfer standard 3.1 The quartz transfer standard is a 100 mm long end block placed in contact with the optical flat. The transfer standard and optical flat are made of the doped quartz glass (pic. 1). 3.2 The steel transfer standard is a 100 mm long end block placed in contact with the optical flat. The transfer standard is made of steel. The optical flat is made of glass (pic. 2). 3.3 The key characteristics of the transfer standards are described in Table 3. Table 3 Characteristic Quartz TS Steel TS Nominal length, mm Coefficient of linear thermal expansion, К -1 0, , Flatness of gauging faces, μm 0,06 0,09 Serial number КС 4475 Е Method of measurement 4.1 Koesters interferometer is a two-beam Michelson interferometer used for absolute measurement of the end block lengths using the method of coincidence of fractional parts of the orders of interference. The fractional part of the order of interference is determined by the shift of interference fringes formed on the gauging face of TS against interference fringes formed on the top surface of the optical flat wrung to the second gauging face of the TS. In the mode of absolute measurement, interference fringes are produced with the light 3

4 from a spectral lamp or laser. To determine the end block length it is necessary to establish a number of interference fringes starting from the surface of the optical flat to which this end block is wrung and up to the central point on the top face of the end block. The direct counting method is not used because it would be a rather complicated procedure and the interference comparator is not designed for it. If we already know the approximate length of the end block, fractional parts only are considered that correspond to the shift in the fringe pattern of the optical flat against the fringe pattern of the gauging face of the end block. The measurements are performed using four well-known optical wavelengths. For each TS length, individual fraction for each of certain wavelengths is established. The so-called target fractions for particular wavelengths and for wavelengths conventionally used to measure end-block lengths are listed in the table attached to the device. The real fractions are values evaluated from optical measurements. The differences between target fractions and real fractions give differential fractions. From differential fractions for wavelengths used, deviation from nominal length for the test end block can be determined. To calculate the length for the test end block, the above deviation should be either added to or subtracted from the nominal length (it depends on whether this deviation is a positive or a negative one). The length, L, of the end block with mutually parallel flat gauging faces is defined here as the length of the normal from the given point on the top gauging face to its opposite face, which is thoroughly cleaned and wrung, without any special intermediate material, to the optical flat made of the same material and having the equal surface finish qualities. If this condition is met, the measuring force is equal to zero. Following this condition, in order to ensure that the length measurement result is correct, the end block should be wrung to the optical flat made of the same material as the end block itself. If it is the case, correction for materials heterogeneity will be equal to 0. 5 Measurement conditions 5.1 The conditions used for transfer standards measurements are described in Table 4. Table 4 Conditions Target value Temperature of the TS, С 20 ± 1 Temperature of the air, С 20 ± 1 Relative humidity, % 58 ± 20 4

5 6 Measurement standards BelGIM, Belarus Picture 3 Picture 4 The measurement standard includes: Koesters interferometers (see picture 3); gas-discharge natural krypton, cadmium-114 and helium lamps; interference pattern registration and processing systems (see picture 4); device to measure the temperature of test end block; thermometers, graduated in 0,02 С; cistern mercury barometer; psychrometer with thermometers graduated in 0,2 С; system for measuring the temperature of the TS, including Dewar vessel with thermometers graduated in 0,01 С; thermometer graduated in 0,5 С; potentiometer type Р 348; normal element; amplifier type F305.2; chromel-copel thermocouple; DC voltage regulator type П36-2; currentreverser, type П309; current reverser used to avoid thermoelectric effect, type ПБ-12В; steel transfer standard, 100 mm, no Е-1606; quartz transfer standard, 100 mm, no кс4475. GUM, Poland Picture 5 Picture 6 5

6 The measurement standard includes: Koesters interferometers (see picture 5); gas-discharge cadmium-114 lamps; CCD camera to capture interference fringes from computer to process information (see picture 6); piezoceramics to generate phase step when phase images are captured; multimeter to measure the temperature of transfer standard and air temperature, graduated in 0,001 С; electronic barometer, graduated in 0,01 Pa; humidity meter, graduated in 0,1 %. SMU, Slovakia Picture 7 Picture 8 The measurement standard includes: Koesters interferometers (see picture 7); gas-discharge krypton-86 lamps; mercury barometer type B1, graduated in 0,1 Тоrr (see picture 8); special thermometers, graduated in 0,02 С; aspiration psychrometer type 11С, graduated in 0,2 С. 6

7 KazInMetr, Kazakhstan The measurement standard includes: Koesters interferometer (see picture 9); gas-discharge natural krypton lamps; special thermometers graduated in 0,02 С to measure the temperature of transfer standard and air temperature in the interferometer thermostat; barometer, type БОП-1М-2; aspiration psychrometer, type М-34, with thermometers graduated in 0,2 С. Picture 9 Ukrmetrteststandart, Ukraine The measurement standard includes: Koesters interferometers (see picture 10); gas-discharge cadmium-114 and natural krypton lamps; cistern mercury barometer, type СР-А; special thermometers, graduated in 0,02 С; Picture 10 aspiration psychrometer, with thermometers graduated in 0,2 С; temperature measurement unit, including Dewar vessel with thermometer type ТР-1 graduated in 0,01 С, chromel-copel thermocouple, nanovoltampermeter type Р-341, current reverser used to avoid thermoelectric effect. 7

8 NSC Institute of metrology, Ukraine The measurement standard includes: Koesters interferometer (see picture 11); gas-discharge cadmium-114 and natural krypton lamps; barometer, type ИР; platinum resistance thermometer to measure absolute temperatures copper-constantan thermometer to measure the temperature of transfer standard and air temperature Picture 11 aspiration psychrometer, with thermometers graduated in 0,2 С; 6.1 Comparison of design types and instruments used in the measurement standards Таблица 5 Laboratory Type of interferometer Source of light BelGIM Koesters cadmium-114 gas-discharge lamp (Cd 114) GUM Koesters cadmium-114 gas-discharge lamp (Cd 114) SMU Koesters krypton-86 gas-discharge lamp (Kr 86) Ukrmetrteststandart Koesters cadmium-114 (Cd 114) and natural krypton (Kr 86) gas-discharge lamps NSCIM Koesters cadmium-114 gasdischarge lamp; (Cd 114) He-Ne laser KazInMetr Koesters natural krypton gasdischarge lamp (Kr 86) Registration system Videocamera, computer-aided pattern processing CCD camera with piezoceramics to generate phase step, computeraided pattern processing Visual observation Visual observation Visual observation Visual observation 8

9 7. Mathematical model for measurement 7.1 The length of transfer standard should be calculated with formula where L = L ном + L + L + L t + L o + L (1), L ном is nominal length of TS; L is deviation of length of TS from its nominal length determined from a particular measurement with measurement standard; L is correction for difference between the length of optical wave under measurement conditions and length under normal conditions; L t is correction for thermal deformation of TS; L o is correction for size of the collimator entrance slit; L is correction for heterogeneity between TS material and optical flat material. 8 Results of measurements 8.1 The deviations of measured median length from nominal length of TS obtained by laboratories as well as declared measurement uncertainties are summarized in Tables 6 and Results of measurements of quartz TS: Table 6 Characteristic Deviation of measured median length from nominal length of TS, μm Declared uncertainty U, μm (k=2, Р=95 %) Laboratory BelGIM GUM SMU NCSIM - 3,254-3,256-3,236-3,245-3,247 0,030 0,025 0,034 0,040 0, Results of measurements of steel TS: Table 7 Characteristic Deviation of measured median length from nominal length of TS, μm Declared uncertainty U, μm (k=2, Р=95 %) BelGIM GUM SMU Laboratory NCSIM Ukrmetrteststandart Ukrmetrteststandart Kaz- InMetr +0,247 +0,259 +0,254 +0,251 +0,247 +0,246 0,036 0,025 0,041 0,050 0,040 0,026 9

10 9 Evaluation of measurement results 9.1 The results of measurements performed by participants are evaluated to check d U ( d ) the degree of equivalence between measurement standards (, ). x ref 9.2 The reference value is calculated as a weighted mean value as follows x ref m 1 m p 1 p x (2), where P is weight of the measurement result of laboratory ; x is measurement result of laboratory. p 1 u 2 (3), where u is standard uncertainty declared by laboratory. 9.3 The standard uncertainty of reference value is calculated as follows u 2 x ref N u x (4) 9.4 The degree of equivalence is calculated as follows d x x ref (5) 9.5 The uncertainty of the degree of equivalence is calculated as follows u( d ) u 2 ( x ) u 2 ( x ref ) (6) 9.6 The measurement standards are equivalent, if the following condition is met d 2u ( d ) (7) 10

11 9.7 Evaluation of the degree of equivalence of standards from measurements of quartz TS Table 9 Characteristic Laboratory BelGIM GUM SMU Ukrmetrteststandart NCSIM Deviation of the measured median length from nominal length of the TS, x, μm -3,254-3,256-3,236-3,245-3,247 Declared standard uncertainty, u, μm 0,015 0,013 0,017 0,020 0,020 Reference value, u, μm x ref x ref, μm -3,249 0,007 Difference between measured value and reference value, d, μm -0,005-0,007 0,013 0,004 0,002 U ( d,), μm 0,026 0,022 0,031 0,037 0, The differences between measurement results and reference value for quartz TS as well as associated expanded uncertainties are plotted on figure 11. 0,040 отклонения результатов Differences измерений between от опорного measurement значения и расширенные results and неопределенности reference value этих отклонений and associated expanded uncertainties Ukrmetrtestстстандарт Укрметр- BelGIM БелГИМ GUM SMU теstandart NCSIM 0,030 0,020 мкм μm 0,010 0,000-0,010 reference опорное значение value -0,020-0,030-0,040 Figure 11 11

12 9.8 Evaluation of the degree of equivalence of standards from measurements of steel TS Table 10 Laboratory Characteristic BelGIM GUM SMU Ukrmetr teststand art NCSIM KazInM etr Deviation of the measured median length from nominal length of the TS, x, μm 0,247 0,259 0,254 0,251 0,247 0,246 Declared standard uncertainty, u, μm 0,018 0,013 0,021 0,025 0,020 0,013 Reference value, u, μm x ref x ref, μm 0,251 0,007 Difference between measured value and reference value, d, μm -0,004 0,008 0,003 0,000-0,004-0,005 U ( d,), μm 0,033 0,022 0,040 0,048 0,038 0, The differences between measurement results and reference value for steel TS as well as associated expanded uncertainties are plotted on figure 12. μm мкм 0,040 0,030 0,020 0,010 0,000-0,010-0,020-0,030-0,040 отклонения результатов Differences измерений between от опорного measurement значения и расширенные results and неопределенности reference value этих отклонений and associated expanded uncertainties BelGIM БелГИМ GUM SMU Укрметртестстандарт NCSIM КазИнМетр Ukrmetrteststandart KazInMetr reference опорное value значение Figure Conclusions 10.1 The results of comparison show that the measurement uncertainties are within the declared values. 12

13 10.2 The measurement standards which were compared are equivalent After its publication, this comparison data will support СМСs claimed under L Gauge block End Standards according to the LENGTH classification of services. 13

14 Bibliography 1 ISO/IEC Guide 98-3:2008 (ИСО/МЭК Руководство 98-3:2008) 2 EA 4/02 3 COOMET R/GM/11: COOMET R/GM/14:2006 Uncertainty of measurement -- Part 3: Guide to the expression of uncertainty in measurement (GUM:1995) Expression of the Uncertainty of Measurement in Calibration Regulation on Comparison of Measurement Standards of National Metrology Institutes of COOMET Guide on Estimation of the COOMET Key Comparison Data 14