Bi-lateral Comparison (APMP.L-K ) Calibration of Step Gauge

Transcription

1 APMP ASIA PACIFIC METROLOGY PROGRAMME Asia-Pacific Metrology Programme Bi-lateral Comparison (APMP.L-K ) Calibration of Step Gauge Final Report NMIJ, January 2017

2 Contents 1 Document control 2 Introduction 3 Organization 3.1 Participants 3.2 Details of participants and adjudicator 3.3 Form of comparison 3.4 Schedule 3.5 Handling of the artefact 3.6 Transport of the artefact 4 Artefact 4.1 Description of artefact 4.2 Stability of artefact 5 Measuring instructions 5.1 Measurands 5.2 Measurement instructions 6 Results 6.1 Results and combined standard uncertainties as reported by participants 6.2 Measurement uncertainties 7 Analysis 7.1 Reference values 7.2 Visualization by simple mean 7.3 Calculation of Degrees of Equivalence 8 Conclusion Reference 2/22

3 1 Document control Version Draft A Issued in September Version Draft B1 Issued in October Version Draft B2 Issued in November Version Draft B3 Issued in January Introduction The metrological equivalence of national measurement standards will be determined by a set of key comparisons chosen and organised by the Consultative Committees of the CIPM working closely with the Regional Metrology Organizations (RMOs). APMP regional comparison is now be held. Both the CCL and the Regional comparisons will establish equivalence with National Metrology Institutes throughout the world. In 2012, NMIJ (National Metrology Institute of Japan) and NPLI (National Physical Laboratory in India) agreed upon their performing a bi-lateral comparison on step gauge measurements. The technical protocol has been drawn by NMIJ and it proposes to start the bi-lateral comparison before August The APMP-TCL vice chair acts as an adjudicator of the comparison. The procedure follows the guidelines established by the BIPM [1]. 3 Organization 3.1 Participants As previously stated in the Introduction, The list of participants has been decided according to agreement between NMIJ and NPLI, i.e. the participants are these two bodies who have been the APMP members. The adjudicator is requested for this bilateral comparison. All participants must be able to demonstrate independent traceability to the realization of the metre. By their declared intention to participate in this comparison, the laboratories accept the general instructions and the technical protocol written down in this document and commit themselves to follow the procedures strictly. Once the protocol and list of participants has been agreed, no change to the protocol or list of participants may be made without prior agreement of all participants. 3.2 Details of participants and adjudicator Adjudicator: Contact Person A. Praba Drijarkara National Metrology Institute Address Research and Development Center for Calibration, Instrumentation and Metrology (RCM-LIPI 1 ) Metrology Division Komplex Puspiptek, Serpong-Tangerang 15314, Indonesia Tel. Tel: , ext probo@kim.lipi.go.id 1 At the time of participation, RCM-LIPI was named KIM-LIPI. 3/22

4 k APMP: Virendra Babu Pilot: Abe Makoto National Physical Laboratory Standards of Dimension, Apex Level Standards & Industrial Metrology Dr. K.S.Krishnan Marg, New Delhi , India National Metrology Institute of Japan (NMIJ/AIST) AIST Tsukuba Central 3, Umezono, Tsukuba, Ibaraki , Japan Tel: ia.ernet.in Tel: , Fax : o.jp 3.3 Form of comparison The comparison was conducted in a sequence by its starting and finishing at the pilot laboratory. NMIJ has acted as the pilot laboratory. All results were to be communicated directly to the pilot laboratory as soon as possible and certainly within 6 weeks of completion of the measurements by a laboratory. The stability of the step gauge was assessed by measurements made at NMIJ before and after the circulation of the step gauge. Each laboratory received the step gauge in turn, according to the pre-agreed timetable. A final set of measurements was made at the end of the comparison by the pilot laboratory. Each laboratory had at least four weeks for calibration and transportation. With its confirmation to participate, each laboratory had confirmed that it was capable of performing the measurements in the time allocated to it. It guaranteed that the standards arrived in the country of the next participant at the beginning of the next four weeks period. If for some reasons, the measurement facility was not ready or customs clearance took too much time in a country, the laboratory had to contact the pilot laboratory immediately and according to the arrangement made - eventually to send the standard directly to the next participant before finishing the measurements or even without doing any measurements. If possible the laboratory would be sent the artefact at the end of the comparison. 3.4 Schedule The comparison lasted from August 2012 to May There were some delays due to that of custom clearance and transportation. The last measurement result was received through the adjudicator in November Table 1 Time schedule Region NMI Country Date APMP NMIJ (Facility-1) Japan August /22

5 APMP NPLI India September 2012 APMP NMIJ (Facility-2) Japan February 2013 Return to pilot laboratory NMIJ (Facility-1) Japan May Handling of the artefact The step gauge should be examined immediately upon receipt. The condition of the step gauge should be noted and communicated to the pilot laboratory. The step gauge should only be handled by authorised persons and stored in such a way as to prevent damage. The step gauge should be examined before despatch and any change in condition during the measurement at each laboratory should be communicated to the pilot laboratory. Laboratories should inform the pilot laboratory and the next laboratory via fax or e- mail when the step gauge was about to be sent to the next recipient. Before and after the measurements, the step gauge had to be cleaned. Laboratories are requested to ensure that the content of the package was completed before shipment and to use the original packaging. 3.6 Transport of the artefact It is of utmost importance that the step gauge be transported in a manner in which it will not be lost, damaged or handled by un-authorised persons. The step gauge will be stored in a storage box, and the storage box is stored in a wooden shipping container. Packaging for the artefact has been made which will be suitably robust to protect the artefacts from being deformed or damaged during transit. The step gauge should be sent via courier or delivery company. It should be marked as Fragile and Handle with care. The step gauge should be accompanied by documentation identifying the items uniquely. The packaging is lockable e.g. by clasp, but is easy to open with minimum delay to allow customs inspections to take place. Transportation is each laboratory s responsibility and cost. Each participating laboratory covers the costs for its own measurements, transportation and any customs charges as well as for any damages that may have occurred within its country. The overall costs for the organisation and for the devices are covered by the organising pilot laboratory. The pilot laboratory has no insurance for any loss or damage of the standard during transportation. 4 Artefact 4.1 Description of artefact The measurement artefact is a Mitutoyo step gauge, steel frame, steel gauges, 1010 mm nominal length, thermal expansion coefficient α = K -1. 5/22

6 (Serial No. : , 10 mm steps, 102 contact faces, Manufacturer : Mitutoyo) ) 8 7 ( Support po int Support po int Fig.1: Drawing of the Mitutoyo step gauge 4.2 Stability of artefact Two calibrations were performed by the pilot laboratory in August 2012 and in May The following graph shows the differences from data of August Although a slight linear trend in longitudinal dimension was observed it could be stated that no significant change was recorded. The observed differences were smaller than the measurement uncertainty of the pilot. For further analysis and determination of the reference value, the data obtained in August 2012 was adopted as data of the pilot. 6/22

7 Figure 2 Difference between pilot calibrations of step gauge from August 2012 to May Measuring instructions 5.1 Measurands The measurands of the step gauge are the distances between centre points of the gauge surfaces with its nominal cross section of 9 mm by 10 mm of the rectangular area. 5.2 Measurement instructions The goal of this APMP comparison is to demonstrate the equivalence of routine calibration service for length measurements offered by NMIs to clients, as listed by them in Appendix C of the BIPM Mutual Recognition Agreement (MRA). To this end, participants in this comparison agree to use the same apparatus and methods as routinely applied when calibrating artefacts for clients. Participants are free to tune and operate their systems to best-measurement performance and to take any extra measurements needed to produce a best measurement result, provided that these extra efforts would also be available to a client if requested. Before calibration, the step gauge must carefully be inspected for damage to the measurement surfaces. Any scratches, rusty spots or other damages have to be documented. The step gauge shall be supported in the Bessel points as schematically drawn in figure 1 in any case during the measurement and additionally be clamped if necessary in the same Bessel points. Clamping force applied on the step gauge shall not be greater than needed strength to avoid un-expected deformation. The alignment of the step gauge is done by following instructions described in this clause. If a different alignment procedure is preferred by a laboratory or needed because of equipment constraints then please document it together with the results. The measurements shall be carried out as close as possible both to the centre point at respective gauge surfaces, and as inline as possible to the reference gauging direction. Terms used for the alignment described in this clause are defined as follows. The centre point of the gauge surface: An intersection point of the nominal gauge plane and the centre line. 7/22

8 The nominal gauge plane: An ideal plane virtually existing on intended design of the step gauge. Therefore the nominal gauge planes are all parallel each other and equi-spaced by 10 mm distance in the longitudinal direction one after another. The centre line: A single line passing through the reference gauge centre point and directing the reference gauging direction. The reference gauge centre point: A centre point of the gauge surface at 20 mm longitudinal position on the 2nd gauging pin. The reference gauging direction: A normal vector of the gauge surface at 0 mm longitudinal position on the 1st gauging pin. The nominal dimension of the gauging pin is 9 mm in the width and 10 mm in the height. Therefore the reference gauge centre point is practically realized as an intersection point of: (1) a plane representing the gauge surface at 20 mm longitudinal position on the 2nd gauging pin, (2) a plane located at 4.5 mm below the top side surface, and (3) a plane located at the middle of the right and left side surface. The measurement results have to be appropriately corrected to the reference temperature of 20 C using the values of the thermal expansion coefficient provided. Laboratories should report the temperatures at which the length measurements were made. Laboratories should only measure the artefact at a temperature close to 20 C. No other measurements are to be attempted by the participants and the step gauge should not be used for any purpose other than described in this document. The artefact may not be given to any party other than the participants in the comparison. If for any reason a laboratory is not able to measure all positions of gauges on the step, it is still encouraged to report as much results as it can. 8/22

9 6 Results 6.1 Results and combined standard uncertainties as reported by participants All participants have reported the measurement results. Following table 2 and table 3 respectively show measurement results and the associated combined standard uncertainties reported by participants. A code instead of the full name of the participant has been used to identify the participants to avoid complexity in the graphs and tables. Face NMIJ : Pilot Facility-1 (Lab A) Table 2 NMIJ : Pilot Facility-1 (after circulation) Measurement results NPL India (Lab B) NMIJ (unit : mm) Facility-2 (Lab C) /22

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12 Face Table 3 NMIJ : Pilot Facility-1 (Lab A) Reported combined standard uncertainties (k=1) NMIJ : Pilot Facility-1 (after circulation) NPL India (Lab B) NMIJ (unit : µm) Facility-2 (Lab C) /22

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15 Measurement results and the associated expanded uncertainties (k=2) are graphically represented as Fig. 3, 4, 5, and 6 respectively for that from Lab. A (Pilot), Lab. A (after circulation), B, and C. Fig. 3 Reported results represented as deviation from nominal length and associated expanded uncertainties (k=2), Lab. A (Pilot) Fig. 4 Reported results represented as deviation from nominal length and associated expanded uncertainties (k=2), Lab. A (after circulation) 15/22

16 Fig. 5 Reported results represented as deviation from nominal length and associated expanded uncertainties (k=2), Lab. B Fig. 6 Reported results represented as deviation from nominal length and associated expanded uncertainties (k=2), Lab. C 6.2 Measurement uncertainties Independent from combined standard uncertainties from participants as shown in table 3, Range based measurement uncertainty was reported from participants. Table 4 summarizes them. Table 4 Range based measurement uncertainty reported by participants Participants Reported range based uncertainty Coverage factor Lab. A, (Pilot) Q [ 0.076, x 10-3 x L ] µm, L in mm k=1 Lab. A, (after circulation) Q [ 0.051, x 10-3 x L ] µm, L in mm k=1 Lab. B Q [ 0.227, x 10-3 x L ] µm, L in mm k=1 Lab. C Q [ 0.046, x 10-3 x L ] µm, L in mm k=1 16/22

17 7 Analysis 7.1 Reference values Measurement result reported from the pilot, Lab. A before the artefact circulation was determined to be the reference values within the comparison. CMC of Lab. A was demonstrated by the final report of the Key Comparison APMP.L-K [2]. The reported measurement values by participants Lab. B and that by Lab. C are each separately compared with the reference values to calculate the Degrees of Equivalence. 7.2 Visualization by simple mean Deviation around simple mean calculated from all the reported results was shown in Fig. 7 for visualization purpose. All the reported results lie in range of 1.12 µm. Fig. 7 Visualized reported results around simple mean 7.3 Calculation of Degrees of Equivalence Degrees of equivalence are calculated by a pair of values deviation from the reference value and expanded uncertainty with the coverage factor of k=2, for respective faces with index of =1,2,,101 as shown in table 5. Where and are calculated using equation (1) and (2). The value at the face with the index is calculated using equation (3). Red character is used for a result showing the value exceeding the upper limit of plus unity or the lower limit of minus unity. =, (1) =2 +, (2) = (3) 17/22

18 Face Table 5 Deviation from reference value, expanded uncertainty, and En value NPL India NMIJ Facility-2 (Lab. B) (Lab. C) n (unit : µm) (unit : µm) (unit : µm) (unit : µm) n 18/22

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21 Figure 8, and 9 show graphical representation of degrees of equivalence of Lab. B and C respectively. Fig.8 Degrees of equivalence of Lab. B Fig.7 Degrees of equivalence of Lab. C 8 Conclusion This supplemental comparison was performed by two laboratories with three facilities involved. Comparison lasted one year from August 2012 to May There was no significant deterioration in the step gauge observed although the pilot laboratory observed slight change of about 0.15 µm in the measurement result between two measurements, one performed before the circulation the other performed after the circulation. The step gauge consisted of 102 nominally parallel planes with which 51 planes are facing to positive direction and the other 51 planes are in negative direction were 21/22

22 circulated for this comparison. Measurand is distance between a reference plane and the other plane to be measured. Degree of equivalency was examined. Two quantity values namely, deviation from reference value, and the expanded uncertainty with the coverage factor of k=2 were obtained. En value based on these two quantity values were also calculated to visualize the result. NPLI reported smaller uncertainty than their claimed CMC. It was likely to result underestimation of the uncertainty. If their measurement uncertainty registered in KCDB was used, their En values were smaller than unity and their measurement capability could be confirmed. Measurement results reported by NMIJ sufficiently lie in range within En value of unity, although the overall comparison results were not able to demonstrate calibration capability. It is recommended to the participants to take part in possibly upcoming inter comparison, rather than taking the immediate corrective action. Reference [1] T.J.Quinn, Guidelines for key comparisons carried out by Consultative Committees, BIPM, Paris [2] Final report of APMP.L-K5.2006, End of the report 22/22