COOMET Project 277/UA/03 COOMET L.S-1 Conducting of comparisons of comparators with photoelectric microscopes. Final report

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1 1 COOMET Project 77/UA/03 COOMET L.S-1 Conducting of comparisons of comparators with photoelectric microscopes Final report National Scientific Centre "Institute of metrology" (NSC IM) Coordinator: V. Kupko NSC "Institute of metrology" 4 Mironositskaya Str Kharkov UKRAINE Tel.: kupko@metrology.kharkov.ua Kharkov

2 Report About the results of comparisons of comparators with photoelectric microscopes 1. Introduction on COOMET Project 77/UA/03 (COOMET L.S-1) The aim of the project is comparison of measurement standard instruments of measurement technology for determining the uncertainties and providing reliability of measurement of linear dimensions. Date of registration of the project "Comparisons of comparators with photoelectric microscopes" is 6 June 005. Type of comparisons supplementary. NMIs from three countries were participants of the COOMET project 77/UA/03.. Participants of comparisons: NMI, address of NMI Сontact person Telephone, National Scientific Centre "Institute of metrology" address: 4 Mironositskaya Str Kharkov UKRAINE tel: fax: Republican governmental enterprise Kazakhstan Institute of Metrology (KazInMetr) address: Left bank of the River Ishim, Orynbor Str., 11, , Astana, Kazakhstan Federal state unitary enterprise D.I.Mendeleyev VNIIM address: Russia, St. Petersburg, Moskovsky pr., 19. Vladimir Kupko tel.: kupko@metrology.kharkov.ua Chingis Kuanbaev tel.: chihas@mail.ru Constantine Chekirda tel.: 7 (81) KVchekirda@vniim.ru Ukraine, the coordinator country, developed the program of comparisons and provided comparison measures.

3 3 3. Organization of comparisons. 3.1 Comparisons are conducted on national measurement standard instruments of the highest accuracy by means of interference method with the application of photoelectric microscopes for aiming at the line center. Comparisons were conducted by means of radial method. 3. Dates of conducting of measurements by the participants of comparisons are shown in table 1. NSC Institute of Metrology October 008 D.I.Mendeleyev VNIIM February 009 KazInMetr February 010 NSC Institute of Metrology September Comparison measure in transport box is transferred by messenger service by aerial or surface kind of transport. Expenses for transporting and clearing from customs office are covered by member country of the comparisons. Having conducted the whole phase of comparisons on comparison program member country sends comparison measure to NSC Institute of metrology, Kharkov, Ukraine. 3.4 Comparison measure length measure of metre of МС type, factory number manufactured of invarstabil 58 % Ni, overall dimension *5*30 mm. Mass of comparison measure 3.13 kg. Comparison measure represents H-shaped index grating with nominal length of the main scale of 1000 mm. The length of the interval of the main scale is 1 mm. The width of the strokes of the scale, marked on the neutral surface of the measure is approximately 5 mkm. On the measure scale surface there marked longitudinal axial lines with the distance of mm between them. On the comparison measure there are also two supplementary scales, located at the beginning and at the end of the main scale. The lengths of supplementary scales are 1mm, and the length of the interval of main scales is 0.1 mm. On the lateral surface of a comparison measure there are two marks corresponding to Bessel points (l

4 4 = 0. L, where l distance from the measure edge to the mark, and L distance between measure edges). Temperature coefficient of comparison measure linear expansion is α t = К -1 (1) Measurement standard line comparison measure is placed into original case which is mounted in plywood package when transporting. 4. Methodology of conducting measurements Measurand is the shortest distance between the axis (center) 0 of measure line and the axis (center) of the line of measurable interval. Measuring of interval length should be conducted in the field between two longitudinal axial lines, marked on the surface of the scale of comparison measure (see 3.4.). In table there given nominal values of the intervals, which should be measured. Nominal length of intervals in mm Table When measuring the lengths of any scale interval of comparison measure it s necessary to apply not less than two measuring techniques it s necessary to conduct measurements under forward and return stroke of the comparator carriage with the return to the initial line. The mean value of these two measurements is accepted as measuring result. The measured length of the interval should be reduced to the temperature of 0 C. When measuring it s necessary to place the comparison measure onto the beds in Bessel points, which are pointed out at the measure (see 3.4.). The results of comparisons are recorded with the indication of:

5 5 - brief description of the method and the conditions of conducting of the measurements; - measured values of lengths of the intervals and their deflection from nominal value of length of the interval; - uncertainty budget; 5. Measuring equipment, conditions and measurement results 5.1 NSC Institute of metrology, Ukraine Measuring equipment The measurements were conducted on an interference comparator, placed in a heat chamber, by the method of counting of interference lines. Comparator enters into the composition of national primary measurement standard of length unit metre of DETU For aiming at the line centre, photoelectric microscope with scanning slot was used. As a source of measurement standard emission, He-Ne laser-heterodyne was used, stabilized under the frequency with He-Ne/J laser which wavelength is compared with the wave of He-Ne/J lasers, entering into group measurement standard of a complex of laser sources of measurement standard emission of primary measurement standard of length unit of DETU Relative uncertainty of wavelength of He-Ne laserheterodyne is The refractive index of air is calculated with a help of Edlen formula using measured physical parameters of air: humidity, pressure and temperature. Air humidity was measured with a help of aspiration psychrometer МV-4М. Measurement uncertainty of air absolute humidity is 0.9 mm of mercury. Air pressure was measured with a help of mercury barometer IR. Measurement uncertainty of air pressure is 0.1 mm of mercury. Air temperature and comparison measure was measured with a help of copperconstantan thermocouples cold ends of which are placed on a copper plate.

6 6 Absolute temperature of copper plate is measured with a help of platinum resistance thermometer, calibrated through two reference temperature points water triple point of 0.01 С and helium melting temperature of С. Measurement uncertainty of temperature is С Conditions of conducting of measurements Measurements were conducted under following conditions: -air temperature -air absolute humidity -atmospheric pressure Measurement results (0 ± 0,1) С; (10 ± 3) mm of mercury; (98 10) Kpa; Measurement results of intervals of comparison measure, conducted at NSC Institute of metrology in October 008 and 010 are given in table 3. Table 3. Measurement results of comparison measurement standard intervals. nominal of interval, in mm deviation from nominal nm, 008 deviation from nominal nm, 010 nominal of interval, in mm deviation from nominal nm, 008 deviation from nominal nm,

7 The length of intervals of comparison measure, reduced to 0 С is calculated on the basis of measurement equation () where L N /16 n L (0 0 0 B nom L 0 interval length of comparison measure, reduced to 0 С; N interferometer reading; λ 0 laser emission wavelength in vacuum; 1 16 interferometer constant; n a wavelength refractive index in air; L nom measurement interval nominal length; α measure linear expansion temperature coefficient; Т м temperature of measure. Uncertainty budget, calculated on the basis of formula () is shown in table 4. Sources of uncertainty Identification of line center u(lc) Form variations of line u(lf) Uncertainty of type A, dependent on length of the interval Wavelength (relative) u(λ) Air temperature u(t) Air pressure u(p) Air humidity u(e) Calculation method of refractive index of air u(n) Type of uncertainty Distribution Table 4. Uncertainty budget. Standard uncertainty T м ) Influence coefficient Contribution to total uncertainty nm Independent on length of the interval of type А normal Dependent on length of the interval of type А normal 40 L L L C L 5.7 L 0.1 mm of mercury 0.9 mm of mercury L 43.7 L L 16. L L L 7

8 Temperature of measure Gradient of measure temperature TKLR uncertainty of measure when (0 Т=0.1) С C L 68. L 0,009 C L 10. L L 10 L 8 L length of measuring interval in metres. Total measurement standard uncertainty of interval length, subject to the evaluations shown in table 4, consists of: - total measurement standard uncertainty, independent on the length of the interval: u nm (3) tu - total measurement standard uncertainty, dependent on the length of the interval: u сз (40 0,3 5,7 43,7 16, 50 68, 10, 10 )L 144L nm (4) Total measurement standard uncertainty of the length of the interval subject to the dependent and independent on the length components will be of the form: u c ( u ) (u ) 9,8 (144 L) nm, (5) tu сз where L length of measuring interval in metres. Expanded uncertainty U, when confidence probability equals to 0.95, is calculated by the formula U k 0, 95 u c U with k =. 9,8 (144 ) nm, where L - in metres. (6) 0,95 L 5. Federal state unitary enterprise D.I.Mendeleyev VNIIM, Russia Measuring equipment Measurements were conducted on the interference comparator. The comparator enters into the composition of national primary measurement standard of length unit metre of GET -85. Structure of the interference comparator 1. Frequency-stabilized laser.

9 9. Laser interferometer. 3. Carriage movable on a bed. 4. Carriage drive. 5. System of measurement of temperature of measure, including platinum thermometer and thermocouples. 6. System of thermostating of room. 7. Microscope with CCD camera. 8. Refractometer with vacuum system. 9. Computer with software. Refractive index of air (n) is determined with a help of refractometer on the basis of wavelength of laser (λ ο ) in vacuum, length of camera of refractometer (L ref ) and phase shift of interference fringes (φ ref ) when vacuumizing camera by the formula: n l 0 ref / L ref (7) In the process of calculating the length of intervals of comparison measure, arithmetic mean value of refractive index of air (n a ) is used, measured before and after the measurement. Relative uncertainty of measurement of refractive index of air is Temperature of measure (Т м ) is determined with a help of platinum resistance thermometer and thermocouples. In the process of calculating of length of intervals of comparison measure, arithmetic mean value (Т м ) of temperature of measure is used, changed before and after the measurement. Uncertainty of measurement of measure temperature is С Conditions of conducting measurements When measuring the following conditions were respected: -air temperature (0 ± 0,1) С; -relative humidity of air (58 ± 5) mm of mercury; -atmospheric pressure ( ) Kpa; Measurement results

10 Measurement results of intervals of comparison measurement standard, conducted in Federal state unitary enterprise D.I.Mendeleyev VNIIM in February 009, are shown in table 4. Table 4. Measurement results of intervals of comparison measurement standard nominal of interval, мм deviation from nominal nm, 009 nominal of interval, мм deviation from nominal nm, The length of intervals of comparison measure, reduced to 0 С, is calculated on the basis of measurement equation (8): L erf )/ n ( ( )/ n ) (0 ) (8) 0 ( 0 int B 0 interf B Tм where L 0 length of interval, reduced to 0 С; λ ο length of wave of laser emission in vacuum; φ interf phase shift of interference fringes in interferometer in the process of moving the carriage with microscope; n a refractive index of wave length in air; α temperature coefficient of linear expansion of measure;

11 Т м temperature of measure. Uncertainty budget calculated on the basis of formula (8) is shown in table 5. Sources of uncertainty Identification of line center Inaccuracy of manufacturing of optics Nonlinearity of interferometer Vibration of line edge Evaluation of Type A at maximum interval (vibration, wavelength, electronic noise) Uncertainty of laser wavelength (relative) Refractive index of air (relative) Temperature of measure C Gradient of temperature of measure C Type of uncertainty Distribution Table 5. Uncertainty budget. Measurement standard uncertainty Influence coefficient 11 Contribution to total uncertainty nm Independent on length of the interval of type А normal Dependent on length of the interval of type А normal 30 L 10 8 L L L L L 68. L 0, L 68. L Uncertainty TKLR of measure when (0 Т=0.1) С L 10 L L length of measurable interval in metres. Total measurement standard uncertainty of interval length, with a glance of evaluations shown in table 5, consists of: - total measurement standard uncertainty independent on interval length: u ,3 nm (9) tu - total measurement standard uncertainty, dependent on interval length: u сз ( ) L 137 L nm (10)

12 1 Total measurement standard uncertainty of interval length with a glance of dependent and independent on the length of components will be like u с ( u ) ( u ) 9 (137 L) nm, (11) tu where L length of measurable interval in metres. Expanded uncertainty U with confidence probability equivalent to 0.95, is calculated with a help of the formula U 0,95 = k u c when k =. сз U 9 (137 L) nm, where L in metres. (1) 0, Republican governmental enterprise Kazakhstan Institute of Metrology (KazInMetr) Measuring equipment Measurements were conducted by absolute interference method on interference comparator. Comparator enters into the composition of national primary measurement standard of length unit metre. Into the composition of national primary measurement standard of length unit also enters He-Ne/J with relative frequency instability of Interference comparator consists of: - optic-mechanical system; - frequency-stabilized He-Ne laser of LGN-303 type; - system of measurement of air parameters temperature, pressure, humidity. Relative uncertainty of wavelength of He-Ne laser is 10-8, uncertainty of measurement of temperature of measure equals to 0.01 С, uncertainty of measurement of air parameters are: - temperature 0.01 С; - pressure 0.09 mm of mercury; - humidity 0. mm of mercury; 5.3. Measurement conditions When measuring the following conditions were respected: - air temperature (0 ± 0.1) С;

13 - relative humidity of air (0 ± 5) %; - atmospheric pressure (980 ± 10) Kpa Measurement results Measurement results of comparison measurement standard intervals, conducted at Republican governmental enterprise Kazakhstan Institute of Metrology (KazInMetr) in February 010, are shown in table 6. Table 6. Measurement results of comparison measurement standard intervals nominal of interval, мм deviation from nominal nm, 010 nominal of interval, мм deviation from nominal nm, Length of comparison measurement standard intervals, reduced to 0 С is calculated on the basis of measurement equation (13): where L 0 length of interval, reduced to 0 С; λ ο laser emission wavelength in vacuum; L erf )/ n ( ( )/ n ) (0 ) (13) 0 ( 0 int a 0 interf a Tм

14 φ interf interference lines phase shift in interferometer in the process of moving carriage with microscope; Uncertainty components Identification of center of line u(цш) Nonidealness of optics Nonlinearity of interferometer Variations of line edges Uncertainty of type A,, when measuring big intervals Laser wavelength (relative) Edlen formula (relative) Air pressure mm of mercury Air temperature C n a wavelength refractive index in air; α measure linear expansion temperature coefficient; Т м temperature of measure. Uncertainty budget calculated on the basis of formula is shown in table 7. Type of uncertainty Distribution Table 7. Uncertainty budget Standard uncertainty Influence coefficient Contribution to total uncertainty nm Independent on length of the interval Of type А normal Dependent on length of the interval Of type А normal 40 L 10 8 L L L L L 3.8 L , L 11.4 L 14 Air humidity mm of mercury L 11. L Gradient of measure temperature С Temperature of measure С TKLR uncertainty of measure when (0 Т=0.1) С L 136 L L 136 L L 10 L L length of measurable interval in metres.

15 15 Total measurement standard uncertainty, with a glance of uncertainty evaluations of type A and B, independent on interval length, equals to: u nm (14) tu Total measurement standard uncertainty, with a glance of uncertainty evaluations of type A and B, dependent on interval length, equals to: u сз ( ,8 11,4 11, ) L 07 L nm (15) Then total measurement standard uncertainty will be equivalent to: u с ( u ) ( u ) 15 (07 L) nm, (16) tu сз Expanded uncertainty U, when confidence probability equals to 0.95 is calculated with a help of formula U 0,95 = k u c when k =. U u 15 (07 L) nm, where L in metres. (17) 0,95 с 6. Analysis of measurement results when conducting comparisons. Total time on comparisons is years. During this time comparison measure was transported for times at rather significant distances. At figures 1, and 3 measurement results of comparison measure in 008 and 010 are shown. At these figures there are given deviations of measured intervals from their normal value, with corresponding to them expanded uncertainties. From given data one can make a conclusion that stability of comparison measure for these years is satisfactory. At figures 4, 5 and 6 results obtained from 3 national metrology centers, participants in conducting comparisons were given. Each organization presented its calculation of uncertainties of type A and of type B, which are given in corresponding tables.

16 Measuring of comparison measure of NSC Institute of metrology 16

17 Measurement result obtained by Member countries нм Russia Kazakhstan Ukraine мм Figure 6: Interval мм