AFRIMETS L.S3 Final report Calibration of Gauge Blocks by Mechanical Comparison Method
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AFRIMETS Secretariat Private Bag X34 Lynnwood Ridge 0040
AFRIMETS
Supplementary Comparison Programme
Calibration of Gauge Blocks
by Mechanical Comparison Method
AFRIMETS.L–S3
Final Report Giza, Egypt, March 2015 M. Amer, F. Abdel Aziz
AFRIMETS L.S3 Final report Calibration of Gauge Blocks by Mechanical Comparison Method
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Contents Page No.
Abstract ................................................................................................................................. 3
1. Introduction ......................................................................................................................... 3
2. Aim of the Programme ........................................................................................................ 4
3. Participants .......................................................................................................................... 4
4. Design of the Programme ................................................................................................... 4
5. Reporting .............................................................................................................................. 6
6. Measurement equipment used by the participants ........................................................... 6
7. Stability of the travelling standards ................................................................................... 6
8. Analysis of results ................................................................................................................. 9
9. Reference Values ................................................................................................................ 11
10. Results as reported by the Participants ......................................................................... 12
11. Discussion of measurements results ............................................................................... 18
12. Conclusions ....................................................................................................................... 21
13. List of References ............................................................................................................. 21
AFRIMETS L.S3 Final report Calibration of Gauge Blocks by Mechanical Comparison Method
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Abstract:
A round robin comparison in calibration of gauge blocks by mechanical comparison method
between NMIs of Arab countries in addition to the NMI of South Africa was carried out during
the period of November 2011 to July 2013, The Arab Federation for Metrology (AFM)
identification number for this comparison is: ARABMET L.S.1. NIS-Egypt acted as the pilot
laboratory. One set of gauge blocks, with nominal size: 1 mm, 5 mm, 10 mm, 40 mm, 90 mm
were circulated. This comparison was registered in the BIPM KCDB in June 2012 as an
AFRIMETS supplementary comparison under the identifier AFRIMETS.L-S3. The results
obtained are represented in this report. Coordination of the programme has been done by the
AFM technical support unit.
1- Introduction:
The Technical Support Unit (TSU) of the Arab Federation for Metrology (AFM) developed a
questionnaire to assist the Arab Metrology Programme ARABMET to develop appropriate
protocols and schedules for an intended intercomparisons schemes. In May 2011 the TSU
distributed the questionnaire among Arab Metrology Institutions. Positive response was
received from 5 Arab NMIs requesting the participation in two fields, namely Length and Mass
Measurements. The comparison programme proposed for length was of the Round Robin type
on Gauge Blocks calibration, up to 100 mm, by mechanical means.
It was then decided that the AFM, the observer member of the Intra-Africa Metrology System
(AFRIMETS), would extend its invitation to the National Metrology Institutes, NMIs to participate
in measurement comparison programmes in the prescribed metrological fields. The comparison
programmes were designed, organized and coordinated by AFM TSU under technical support
of the National Institute for Standards (NIS) of Egypt being an active member of both the
Programme and the Federation at the time. The comparison programme was open for NMIs of
the members and non members Arab states of the Federation. The comparisons were to be
conducted following appropriate measurement protocols.
The objectives of the comparison programmes are to provide the participating laboratories with
the means for comparing their measurement results, opportunities for technical capability
improvements and recognition of Calibration and Measurements Capabilities (CMCs). AFM,
being an observer member of the AFRIMETS, worked through concerned AFRIMETS
authorities to submit the comparison programmes for registration as AFRIMETS supplementary
comparisons on the BIPM KCDB. Thus, the National Metrology Institute of South Africa
(NMISA) has been invited to join the round robin scheme.
Five gauge blocks, with nominal size 1 mm, 5 mm, 10 mm, 40 mm and 90 mm are chosen as
the artifacts for the comparison. All of them are made of steel according to ISO 3650:1998. The
Engineering and Surface Metrology laboratory (ESML) of NIS - Egypt provided the travelling
standards and the comparison protocol. The measurements in this comparison were carried out
from November 2011 to July 2013.
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The measurements were carried out according to a protocol approved by the concerned
Regional Metrology Organization technical authorities, namely AFRIMETS.TCL.
2- Aim of the Programme:
The aim of this comparison is to give confidence in the technical capacity of the AFM members
and non members as a step towards the publication of CMCs in the BIPM KCDB to gain
international Statement of Equivalence in accordance with the mutual recognition arrangement
(CIPM MRA). The participation of NIS - Egypt and NMISA – South Africa would help in
achieving these goals through their active participation in Sub Regional Metrology Organizations
(SRMOs) members of AFRIMETS.
The comparison gives objective evidence on the technical competence of the participated
laboratories, and it assists in identifying opportunities to improve the metrological capacity of the
Laboratories.
3- Participants:
Table 3.1 shows the participating NMIs, their affiliations and the planned time schedule.
Country - Laboratory – Abbreviation
Date Planned Metrology region
1- EGYPT - National Institute of Standards – NIS-ESML
November 2011
Pilot Lab; AFM Member, AFRIMETS Member (NEWMET), APMP associate
member and EURAMET Corresponding Member
2- IRAQ - Central Organisation for Standardisation and
Quality Control - COSQC December 2011 AFM Member
3- SYRIA - National Standards and Calibration Laboratory -
NSCL January 2012
AFM Member and APMP Associate Member
4- JORDAN - Jordan National Metrology Institute - JNMI
February 2012 AFM Member and APMP Associate
Member
5- TUNISIA - Central Laboratory for Testing and Analysis-
Metrology Center - LCAE-CME March 2012 AFRIMETS Member (MAGMET)
6- SOUTH AFRICA - National Metrology Institute of South
Africa - NMISA SOUTH AFRICA - National Metrology Institute of
South Africa - NMISA
April 2012 Coach Lab. – AFRIMETS Member (SADCMET) and APMP Associate
Member
1- EGYPT - National Institute of Standards – NIS-ESML
May 2012
Pilot Lab; AFM Member, AFRIMETS Member (NEWMET), APMP Associate
Member and EURAMET Corresponding Member
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4- Design of the Programme:
The program was designed according to the guidelines for CIPM (Comité International des Poids et Mesures) key comparisons. Five travelling gauge blocks of nominal size 1 mm, 5 mm, 10 mm, 40 mm and 90 mm were provided as artifact by NIS-ESML. They are made of steel according to ISO 3650:1998. The travelling standards were circulated between the participants as shown in table 4.1. As pilot laboratory, NIS-ESML of Egypt determined the length deviation of the travelling standards at the beginning and the end of the comparison.
The transportation sequence and measurements of the travelling standards has been done as shown in figure 4.1. NIS-ESML of Egypt acted as the pilot laboratory regarding the measurements which were conducted starting in November 2011 at NIS-ESML. Then the artifact moved to Institute number 2 and so on. No significant accident has been reported during the comparison. However, the artifacts stayed for a longer period than planned at NIS-ESML at the end of the round waiting for their measurement standard to be calibrated to ensure traceability to SI units.
Serial NMI – Country Artefact Received Report Delivered
1 NIS – Egypt November 2011 15 March 2012
2 COSQC – Iraq 14 December 2011 7 February 2012
3 NSCL – Syria 21 January 2012 26 February 2012
4 JNMI – Jordan 11 March 2012 15 March 2012
5 LCAE – Tunis 6 June 2012 10 December 2012
6 NMISA - South Africa 17 October 2012 16 November 2012
7 NIS – Egypt 30 November 2012 7 July 2013
Table 4.1:- Sequence of the measurements
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Figure (4.1) shows the transportation sequence and measurements of the travelling standards.
5- Reporting:
The measurement results were sent to the AFM in a final report. A list of the equipment used as gauge block comparator, environmental conditions, details of measurement procedure and uncertainty analysis were included as well as the reference standard used in order to see the traceability at each laboratory.
6- Measurement Equipment used by Participants:
Lab Measurement Device Tip material
Tip diameter Measuring Force
Upper
tip
Lower
tip
Upper
tip
Lower
tip
NIS-ESML Mitutoyo, GBCD-250 Tungsten
Carbide 40 mm 10 mm 0.8 N 0.3 N
COSQC MAHR 826 Tungsten
Carbide 3 mm 3 mm 0.75 N 0.6 N
NSCL Tsugami - ECHD Tungsten
Carbide 20 mm - 3.2 N -
JNMI Mitutoyo, GBCD250 Tungsten
Carbide 40 mm 10 mm 0.8 N 0.3 N
LCAE MAHR 826 Tungsten
Carbide 3 mm 3 mm 0.75 N 0.6 N
NMISA TESA Tungsten 40 mm 40 mm 0.63 N 0.63 N
NIS-Egypt
NSCL - Syria
JNMI - Jordan
LCAE - Tunis
NMISA - South Africa
COSQC - Iraq
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Table 6.1.: Measurement equipment used in comparison
7- Stability of the traveling standards:
The pilot laboratory NIS-ESML of Egypt assures the stability of the traveling standards during a period of months before beginning of the laboratory measurements. Statement on the instability has been found, so that, the measured gauge block length values of the traveling standards were stable during this period. The travelling standards were circulated among five participating laboratories without any incident that required any return to the pilot laboratory to re-measure the travelling standards. Figures 7.1 to 7.5 show graphs indicating the stability of gauge blocks.
7.1. Stability of 1 mm gauge block
Figure 7.1. Stability of 1 mm gauge block
7.2. Stability of 5 mm gauge block
-30
-20
-10
0
10
20
30
40
50
Dev
iati
on
fro
m n
om
inal
len
gth
, nm
NIS- Nov.2011 NIS - July 2013
1 mm gauge block
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Figure 7.2. Stability of 5 mm gauge block
7.3. Stability of 10 mm gauge block
Figure 7.3. Stability of 10 mm gauge block
7.4. Stability of 40 mm gauge block
-20
0
20
40
60
80
100
120
Dev
iati
on
fro
m n
om
inal
len
gth
, nm
NIS- Nov.2011 NIS - July 2013
10 mm gauge block
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Figure 7.4. Stability of 40 mm gauge block
7.5. Stability of 90 mm gauge block
Figure 7.5. Stability of 90 mm gauge block
-150
-100
-50
0
50
100
Dev
iati
on
fro
m n
om
inal
len
gth
, nm
NIS- Nov.2011 NIS - July 2013
90 mm gauge block
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8. Analysis of results: The weighted mean is used as the reference value in the comparison. For each laboratory (i) the normalized weight, wi was calculated by the following formula:
𝑤𝑖 = 𝑐.1
𝑢2(𝑥𝑖) (1)
where u(xi) is the standard uncertainty given by the laboratory “i” and C is the normalizing factor and is calculated by the following formula:
𝑐 = 1
∑1
𝑢2(𝑥𝑖)𝑛𝑖=1
(2)
where n is the number of the laboratories. The weighted mean (reference value) is:
�̅�𝑤 = ∑ 𝑤𝑖 . 𝑥𝑖𝑛𝑖=1 (3)
The uncertainty of the deviation from the weighted mean is:
𝑢(𝑥𝑖 − �̅�𝑤) = √𝑢2(𝑥𝑖) − 𝑢𝑖𝑛𝑡2 (�̅�𝑤) (4)
To avoid bias, only the first set of measurements from the pilot laboratory was included in reference value determination and the analysis of the results of each participant can be done by calculating the deviation of the given result from the weighted mean and the uncertainty of this deviation. The statistical consistency of the results with the uncertainties given by the participants can be checked by the En value for each laboratory.
𝐸𝑛 = xi−x̅w
2√u2(xi)−uint2 (x̅w)
(k = 2) (5)
where 𝑥𝑖 − �̅�𝑤 is the deviation from the weighted mean for a result of a laboratory, uint is the so called internal standard deviation that is based on the estimated standard uncertainties as reported by the participants:
𝑢𝑖𝑛𝑡 (�̅�𝑤) = √𝐶 (6)
En values for consistent measurement results are expected to be between -1 and 1 for a coverage factor of k = 2.
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The statistical consistency of the comparison can be analyzed by the so called Birge ratio test. The Birge ratio compares the observed spread of the results with the spread expected from the individual reported uncertainties. The Birge ratio is:
𝑅𝐵 = 𝑢𝑒𝑥𝑡 (�̅�𝑤)
𝑢𝑖𝑛𝑡 (�̅�𝑤) (7)
where uext is the so called external standard deviation and can be calculated by the following formula:
𝑢𝑒𝑥𝑡(�̅�𝑤) = √ 1
𝐼−1 .
∑ (𝑥𝑖−�̅�𝑤)
2
𝑢2(𝑥𝑖)𝐼𝑖=1
∑ 1
𝑢2(𝑥𝑖)𝐼𝑖=1
. (8)
where I is the number of the results that are taken in the calculation.
For an infinite population size, the Birge ratio has an expectation value of RB = 1, when
considering standard uncertainties. For a coverage factor of k = 2, the expectation value is increased and the data in a comparison are consistent provided that
𝑅𝐵 < √1 + √8/(𝐼 − 1) . (9)
For a limited population size, the Birge criterion is given by:
𝑅𝐵 𝐶𝑟𝑖𝑡 = √1 + √8/(𝐼 − 1) (10)
If the calculation of a gauge shows inconsistent dataset, the largest consistent subset is determined by elimination, starting with excluding the result having the largest En value that makes the largest contribution to the overall chi-squared value. The iteration runs until RB < RB crit. For six laboratories, RB is equal to 1.5. The criterion is recalculated if any results are excluded. A Birge ratio much larger than the criterion implies that some data contain systematic offsets or alternately that some uncertainties have been underestimated. A ratio much less than the criterion implies that uncertainties have been overestimated. The results will point to calculations that may need further investigation and possibly reassessment. The reference value will be selected that best reflects the population. For a population with a number of results of En greater than 1 and the Birge ratio greater than the Birge criterion, the result with the largest En was removed and the weighted mean, the
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uncertainty of the mean, all En values, the Birge ratio and Birge criterion were recalculated. This iteration process was repeated until the Birge ratio became less than the Birge criterion and the exclusion process was stopped. When a result xi is excluded from the reference value, it is not correlated to it and its En value is calculated by:
𝐸𝑛 = 𝑥𝑖−�̅�𝑤
2√𝑢2(𝑥𝑖)−𝑢𝑖𝑛𝑡2 (�̅�𝑤)
(11)
9 – Reference Value: In this comparison, to meet the requirements of the Mutual Recognition Arrangement, the Key Comparison Reference Values (KCRV) has been evaluated according to the method described in section 8. The weighted mean was determined and the deviations from the weighted mean were calculated. The uncertainty of the weighted mean is based on the internal standard deviation of the final measurement results. The stability measurements of the gauge blocks, performed by the pilot laboratory were excluded. The results of the pilot laboratory contribute only once in the calculation of the reference values. Table 9.1 shows the Key Comparison Reference Values and their standard uncertainties.
Table 9.1 Key Comparison Reference Values and associated standard uncertainty (k = 1).
Nominal Length
(mm)
Reference value
(nm)
Reference value
uncertainty (nm)
1 25.6 13.7
5 66.2 14.4
10 42.9 15.5
40 -57.2 22.5
90 -55.1 36.5
10 – Results as reported by the Participants:
On receipt of the reports from all participants the coordinator asked the participants to revise their results regarding the units and uncertainties quoted. Among the received answers, the JNMI asked to withdraw the results of 40 mm and 90 mm gauge blocks for technical reasons. This withdrawal of results was made before Draft A was released, i.e. with the results still ‘blind’.
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Overview of measurement results as they were reported by the participating laboratories is given in Table 10.1. Weighted mean and its difference from reported results were calculated, along with corresponding En values (k = 2), for each gauge block. A statistical consistency check was performed as described in section 8. Results of 90 mm gauge block which belongs to COSQC were excluded from calculation in order to form a consistent subset, and their En values are given according to:
𝐸𝑛 = 𝑥𝑖−�̅�𝑤
2√𝑢2(𝑥𝑖)+𝑢𝑖𝑛𝑡2 (�̅�𝑤)
(12)
NIS- ESML
COSQC NSCL JNMI LCAE NMISA
∆L uc ∆L uc ∆L uc ∆L uc ∆L uc ∆L uc
1 mm 10 28.7 50 48.2 34 27 30 90 28 30 20 30
5 mm 70 31.5 80 48.1 53 29 70 90 56 32 80 30
10 mm 60 35.1 20 48.1 47 35 10 90 17 34 60 30
40 mm -40 56.4 -10 48.3 -59 49 NA NA -126 45 -30 55
90 mm -20 91.9 100 49.3 -121 91 NA NA -45 64 -50 61
Table 10.1. Reported measurement results, in nm, k = 1
10.1. Results of 1 mm gauge block
Table 10.1.1. Results as reported by the participants
Nominal
1 mm
NIS- ESML COSQC NSCL JNMI LCAE NMISA
∆L uc ∆L uc ∆L uc ∆L uc ∆L uc ∆L uc
10 28.7 50 48.2 34 27 30 90 28 30 20 30
AFRIMETS L.S3 Final report Calibration of Gauge Blocks by Mechanical Comparison Method
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Figure 10.1.1. Graphical representation of results
Table 10.1.2. Results calculated from participant’s values
1 mm Xi - Xw En
NIS- ESML -15.6 -0.31 uint, nm 13.66
COSQC 24.4 0.26 uext, nm 5.08 NSCL 8.38 0.18 RB 0.37 JNMI 4.38 0.02 Xw, nm 25.62
LCAE 2.38 0.04
NMISA -5.62 -0.11
10.2. Results of 5 mm gauge block
Table 10.2.1. Results as reported by the participants
Nominal
5 mm
NIS-ESML COSQC NSCL JNMI LCAE NMISA
∆L uc ∆L uc ∆L uc ∆L uc ∆L uc ∆L uc
70 31.5 80 48.1 53 29 70 90 56 32 80 30
-80
-60
-40
-20
0
20
40
60
80
100
120
140
160
NIS COSQC NSCL JNMI LCAE NMISA
De
viaa
tio
n f
rom
no
min
al le
ngt
h, n
m 1mm gauge block standard uncertainty (k = 1)
AFRIMETS L.S3 Final report Calibration of Gauge Blocks by Mechanical Comparison Method
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Figure 10.2.1. Graphical representation of results
Table 10.2.2. Results calculated from participant’s values
5 mm Xi - Xw En
NIS- ESML 3.8 0.07 uint, nm 14.38 COSQC 13.8 0.15 uext, nm 5.06 NSCL -13.2 -0.26 RB 0.35 JNMI 3.8 0.02 Xw, nm 66.2
LCAE -10.2 -0.18
NMISA 13.8 0.26
10.3. Results of 10 mm gauge block
Table 10.3.1. Results as reported by the participants
Nominal
10 mm
NIS- ESML COSQC NSCL JNMI LCAE NMISA
∆L uc ∆L uc ∆L uc ∆L uc ∆L uc ∆L uc
60 35.1 20 48.1 47 35 10 90 17 34 60 30
-40
-20
0
20
40
60
80
100
120
140
160
180
200
NIS COSQC NSCL JNMI LCAE NMISA
De
viaa
tio
n f
rom
no
min
al le
ngt
h, n
m 5mm gauge block standard uncertainty (k = 1)
AFRIMETS L.S3 Final report Calibration of Gauge Blocks by Mechanical Comparison Method
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Figure 10.3.1. Graphical representation of results
Table 10.3.2. Results calculated from participant’s values
10 mm Xi - Xw En
NIS- ESML 17.1 0.27 uint, nm 15.51 COSQC -22.9 -0.25 uext, nm 8.54 NSCL 4.1 0.07 RB 0.55 JNMI -32.9 -0.19 Xw, nm 42.9
LCAE -25.9 -0.43
NMISA 17.1 0.33
10.4. Results of 40 mm gauge block
Table 10.4.1. Results as reported by the participants
Nominal
40 mm
NIS- ESML COSQC NSCL JNMI LCAE NMISA
∆L uc ∆L uc ∆L uc ∆L uc ∆L uc ∆L uc
-40 56.4 -10 48.3 -59 49 NA NA -126 45 -30 55
-100
-80
-60
-40
-20
0
20
40
60
80
100
120
140
NIS COSQC NSCL JNMI LCAE NMISA
De
viaa
tio
n f
rom
no
min
al le
ngt
h, n
m 10mm gauge block standard uncertainty (k = 1)
AFRIMETS L.S3 Final report Calibration of Gauge Blocks by Mechanical Comparison Method
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Figure 10.4.1. Graphical representation of results
Table 10.4.2. Results calculated from participant’s values
40 mm Xi - Xw En
NIS- ESML 17.2 0.17 uint, nm 22.45 COSQC 47.2 0.55 uext, nm 21.39
NSCL -1.8 -0.02 RB 0.95 JNMI - - Xw, nm -57.2
LCAE -68.8 -0.88
NMISA 27.23 0.27
10.5. Results of 90 mm gauge block
Table 10.5.1. Results as reported by the participants
Nominal
90 mm
NIS- ESML COSQC NSCL JNMI LCAE NMISA
∆L uc ∆L uc ∆L uc ∆L uc ∆L uc ∆L uc
-20 91.9 100 49.3 -121 91 NA NA -45 64 -50 61
-200
-160
-120
-80
-40
0
40
80
NIS COSQC NSCL JNMI LCAE NMISA
De
viaa
tio
n f
rom
no
min
al le
ngt
h, n
m 40mm gauge block standard uncertainty (k = 1)
AFRIMETS L.S3 Final report Calibration of Gauge Blocks by Mechanical Comparison Method
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Figure 10.5.1. Graphical representation of results for 90 mm gauge block with standard uncertainty
(k = 1)
Table 10.5.2. Results calculated from participants values
90 mm Xi - Xw En
NIS -ESML -19.8 -0.11 uint, nm 29.32 COSQC 100.2 1.27 uext, nm 39.05
NSCL -120.83 -0.70 RB 1.33 JNMI - - Xw, nm -0.17
LCAE -44.83 -0.39
NMISA -49.83 -0.47
Table 10.5.3. Results calculated from largest consistent subset
90 mm Xi - Xw En
NIS - ESML 35.1 0.21 uint, nm 36.47
COSQC 155.1 1.27 uext, nm 17.64 NSCL -65.95 -0.40 RB 0.48 JNMI - - Xw, nm -55.05
LCAE 10.05 0.10
NMISA 5.05 0.05
-260
-220
-180
-140
-100
-60
-20
20
60
100
140
180
220
NIS COSQC NSCL JNMI LCAE NMISA
De
viaa
tio
n f
rom
no
min
al le
ngt
h, n
m 90mm gauge block standard uncertainty (k = 1)
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In table 10.5.2., the results calculated from all the participants’ values. After the statistical consistency check was performed as described in section 8. Results of 90 mm gauge block which belongs to COSQC were excluded from calculation in order to form a consistent subset and the results in table 10.5.3 are calculated.
11 - Discussion of measurement results: Table 11.1 shows the differences of measured values with respect to Key Comparison Reference Values and the expanded (k = 2) uncertainties of these differences, calculated by:
𝑈(𝑥𝑖 − �̅�𝑟𝑒𝑓) = 2√𝑢2(𝑥𝑖) − 𝑢2 (�̅�𝑟𝑒𝑓) (12) where u(xi) is the standard uncertainty of the laboratory result xi and u(xref) is the standard uncertainty of the reference value xref.
Table 11.1 Differences of measured values and KCRV’s, with expanded uncertainties (k = 2)
Gauge block \ Lab NIS – ESML COSQC NSCL JNMI LCAE NMISA
1 mm xi-xref -15.6 24.4 8.4 4.4 2.4 -5.6 U(xi-xref) 50.5 92.4 46.6 177.9 53.4 53.4
5 mm xi-xref 3.8 13.8 -13.19 3.81 -10.19 13.81 U(xi-xref) 56.2 91.8 50.4 177.7 57.2 52.7
10 mm xi-xref 17.1 -22.9 4.13 -32.87 -25.87 17.13 U(xi-xref) 63.0 91.1 62.8 177.3 60.5 51.4
40 mm xi-xref 17.2 47.2 -1.8 --- -68.8 27.2 U(xi-xref) 103.5 85.5 87.1 --- 78.0 100.4
90 mm xi-xref 35.1 155.1 -65.9 --- 10.1 5.1 U(xi-xref) 168.7 122.6 166.7 --- 105.2 97.8
Figures 11.1 through 11.5 show the graphs of Degrees of Equivalence for the five gauge blocks.
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Figure 11.1 Degrees of Equivalence for 1 mm gauge block with expanded uncertainty (k = 2)
Figure 11.2 Degrees of Equivalence for 5 mm gauge block with expanded uncertainty (k = 2)
-200.00
-150.00
-100.00
-50.00
0.00
50.00
100.00
150.00
200.00
250.00
NIS COSQC NSCL JNMI LCAE NMISA
-200
-150
-100
-50
0
50
100
150
200
250
NIS COSQC NSCL JNMI LCAE NMISA
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Figure 11.3 Degrees of Equivalence for 10 mm gauge block with expanded uncertainty (k = 2)
Figure 11.4 Degrees of Equivalence for 40 mm gauge block with expanded uncertainty (k = 2)
-250
-200
-150
-100
-50
0
50
100
150
200
NIS COSQC NSCL JNMI LCAE NMISA
-200
-150
-100
-50
0
50
100
150
200
NIS COSQC NSCL JNMI LCAE NMISA
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Figure 11.5 Degrees of Equivalence for 90 mm gauge block with expanded uncertainty (k = 2)
12 – Conclusion:
Participation of NMISA of South Africa, a non member of Arab Federation for Metrology
(AFM), enriched the inter-comparison programme and contributed to its recognition on
the international level.
Measurements reports provided by participants show a well established scientific
discipline in length metrology in the participant laboratories.
Data, equipments, procedures followed and traceability listed in the participant’s reports
show a very good infra- structure for length metrology in the participant laboratories
except for NSCL where a single probe comparator was used which does not comply with
ISO 3650:1998.
The inter-comparison programme assures the ability of the participant laboratories to
provide a world class results in length metrology except for COSQC for 90 mm gauge
block, also, JNMI does not participate for 40 mm and 90 mm gauge blocks.
13 – List of References
1. ISO 3650:1998(E), Geometrical Product Specification (GPS) – Length Standards –
Gauge Blocks, International Organization for Standardization, Geneva, Switzerland.
2. Guide to the Expression of Uncertainty in Measurement (JCGM 100:2008, GUM 1995
with minor corrections)
3. Decker J.E., Brown N. et al., Recent recommendations of Consultative Committee for
Length (CCL) regarding strategies for evaluating key comparison data. Metrologia 43
(2006) L51-L55.
4. EURAMET comparison of gauge blocks by interferometry, EURAMET
#1138,EURAMET.L-K1.2 ,Final report, Zagreb, December 2011, V. Mudronja, M. Katic.
-200
-150
-100
-50
0
50
100
150
200
250
300
NIS COSQC NSCL JNMI LCAE NMISA
AFRIMETS L.S3 Final report Calibration of Gauge Blocks by Mechanical Comparison Method
23
5. Asia-Pacific Metrology Programme; developing Economies‘ Committee (DEC)
Intercomparison on gauge blocks by Mechanical Comparison Method (APMP.L-S3; 2006
– 2009)
6. Measurement comparisons in the CIPM MRA; CIPM MRA-D-05 Version 1.2.
7. International comparison of surface roughness, APMP.L-K8, final report, NMIA 2013,
Andrew Baker.
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