SUPLEMENTARY COMPARISON IN MASS
SIM/ANDIMET/SURAMET
INSTITUTO BOLIVIANO DE METROLOGÍA (IBMETRO), BOLIVIA
LABORATORIO CUSTODIO DE LOS PATRONES NACIONALES DE MASA EN CESMEC LTDA (CESMEC-LCPN-M),
CHILE
COMPARISON REPORT
1. ABSTRACT
A mass comparison was carried out between the Instituto Boliviano de Metrología (IBMETRO, Bolivia),
and Laboratorio Custodio de los Patrones Nacionales de Masa at Cesmec Ltda. (CESMEC-LCPN-M,
Chile), in order to estimate degrees of equivalence for calibration of a mass artifact and the uncertainty
associated to its measurement.
This comparison was carried out in the following nominal values: 50 g and 1 kg
2. INTRODUCTION
Within the framework of SIM few comparison activities were carried out between the participants of the
present comparison in mass. For this reason we think that this results are interesting for being submitted
to the SIM MWG7.
3. OBJECTIVE
To compare mass measurements at 50 g and 1 kg, estimate degrees of equivalence and levels of
measurement agreement.
4. COMPARISON
4.1 COMPARISON STANDARD
50 g and 1 kg weights of OIML E2 design was provided for this comparison by IBMETRO
Density at 20 °C = 8000 kg/m3
Uncertainty of density (k=2) = 140 kg/m3
Manufacturer: Gottl. Kern & Sohn GmbH, Albstadt, Germany
Serial number: G972368
Marks: none
4.2 COMPARISON ROUND
One initial measurement was performed at IBMETRO and a final measurement at CESMEC-LCPN-M.
IBMETRO
CESMECLCPN-M
2000.05.04
2000.07.12
Page 1 of 5 pages
SUPLEMENTARY COMPARISON IN MASS
SIM/ANDIMET/SURAMET
INSTITUTO BOLIVIANO DE METROLOGÍA (IBMETRO), BOLIVIA
LABORATORIO CUSTODIO DE LOS PATRONES NACIONALES DE MASA EN CESMEC LTDA (CESMEC-LCPN-M),
CHILE
Table 1: Participant laboratories, their standards and measurement schedule.
Laboratory Country
Contact person
Standard
Institute that Date of
performed
measurement
its
calibration
IBMETRO
Bolivia
Mr. Gerson Vallejos
E1 set of
PTB
2000.05.04
gvallejos@ibmetro.org
weights
CESMECChile
Mr. Francisco García
E1 set of
PTB
2000.07.12
LCPN-M
fgarcia@cesmec.cl
weights
(Pilot)
4.3 GENERAL GUIDELINES AND PROCEDURE
Measurements were done after an acclimatization time as specified in OIML R111 Draft for class E1 [1].
No washing was performed. Before measurements, dust particles were removed from the surface of the
standard by a soft brush.
All weightings were performed in air by double substitution method with buoyancy correction ([1], [4])
Uncertainties were estimated and combined according to the ISO Guide to the Expression of Uncertainty
in Measurement [2].
5. RESULTS
Laboratory
Table 2.1:
Mass Value
Results at 50 g
Uncertainty (k=2)
IBMETRO
50 g + 69,58 mg
0,04 mg
CESMEC- LCPN-M
(Pilot)
50 g + 69,574 mg
0,030 mg
Laboratory
IBMETRO
CESMEC- LCPN-M
(Pilot)
Table 2.2:
Mass Value
Results at 1 kg
Uncertainty (k=2)
1 kg + 1,5 mg
0,5 mg
1 kg + 1, 32 mg
0,62 mg
Calibration
Certificate
CC-LM-075-2000
Calibration
Certificate
CC-LM-074-2000
Page 2 of 5 pages
Mass correcttion to the nominal value 50 g
/ mg
SUPLEMENTARY COMPARISON IN MASS
SIM/ANDIMET/SURAMET
INSTITUTO BOLIVIANO DE METROLOGÍA (IBMETRO), BOLIVIA
LABORATORIO CUSTODIO DE LOS PATRONES NACIONALES DE MASA EN CESMEC LTDA (CESMEC-LCPN-M),
CHILE
69,62
69,60
69,58
69,56
69,54
IBMETRO
CESMEC-LCPN-M
Laboratories
Uncertainty bars are for k=2
Mass correcttion to the nominal value 1 kg
/ mg
2,2
2,0
1,8
1,6
1,4
1,2
1,0
0,8
0,6
IBMETRO
CESMEC-LCPN-M
Laboratories
Uncertainty bars are for k=2
Page 3 of 5 pages
SUPLEMENTARY COMPARISON IN MASS
SIM/ANDIMET/SURAMET
INSTITUTO BOLIVIANO DE METROLOGÍA (IBMETRO), BOLIVIA
LABORATORIO CUSTODIO DE LOS PATRONES NACIONALES DE MASA EN CESMEC LTDA (CESMEC-LCPN-M),
CHILE
5. Discussion
5.1 Degrees of equivalence and levels of measurement agreement for pairs of results.
At each nominal value degrees of equivalence are expressed by the pair of terms
d i , j  xi  x j
(1)
U ( d i , j )  U 2 xi   U 2 x j   U t2
(2)
, its expanded uncertainty (k=2).
Where,
xi is the result informed by laboratory i
U xi  is the expanded uncertainty (k=2) of result informed by laboratory i
U t is the uncertainty associated with transportation of the measured device between the laboratories
and is estimated negligible (0 mg)
For the comparison results, the degrees of equivalence are as follows:
Nominal value
d i , j  xi  x j
U ( d i , j )  U 2 xi   U 2 x j   U t2
50 g
1 kg
0,01 mg
0,2 mg
0,05 mg
0,8 mg
In order to evaluate the level of measurement agreement between any pair of results informed by
laboratories (i, j) , the normalized error and criteria stated in [3] is used:
Ei , j 
di,j
U d i , j 
(3)
From (3), we get:
Nominal value
50 g
1 kg
Ei , j 
di,j
U d i , j 
0,20
0,3 mg
Page 4 of 5 pages
SUPLEMENTARY COMPARISON IN MASS
SIM/ANDIMET/SURAMET
INSTITUTO BOLIVIANO DE METROLOGÍA (IBMETRO), BOLIVIA
LABORATORIO CUSTODIO DE LOS PATRONES NACIONALES DE MASA EN CESMEC LTDA (CESMEC-LCPN-M),
CHILE
6. Conclusion
There are satisfactory levels of measurement agreement between results and with respect to the
reference value. Degrees of equivalence are listed in 5.
7. References
1. Committee Draft OIML/2nd CD R 111, OIML/TC 9 / SC 3, 2000
2. Guide To The Expression Of Uncertainty In Measurement; ISO TAG 4 WG 3. BIPM, IEC, IFCC,
ISO, IUPAC, IUPAP, OIML; 1995.
3. Document No. 8, Noramet, 1998.
4. Schwartz, R.: Guide to mass determination with high accuracy, Braunschweig: PhysikalischTechnische Bundesanstalt 1995, PTB-MA-40
Francisco García
Deputy Head
CESMEC-LCPN-M
Date of issue: 2004.12.16
Page 5 of 5 pages