The calibration of a weight of nominal value 10 kg of OIML class M1 is carried out by comparision to a reference standard (OIML class F2) of same nominal value using a mass comparator whose performance characteristics have previously been determined.

Model Equation:

mX = mS + dmD + dm + dmC + dB

List of Quantities:

Quantity	Unit	Definition
mX	g	conventional mass of the unknown
mS	g	conventional mass of the standard
dmD	g	change of value of the standard since its last calibration due to drift
dm	g	observed difference in mass between the unknown mass and the standard
dmC	g	correction for eccentricity and magnetic effects
dB	g	correction for air buoyancy

mS:	Type B normal distribution Value: 10000.005 g Expanded Uncertainty: 45·10-3 g Coverage Factor: 2

REFERENCE STANDARD: The calibration certificate for the reference standard gives a value of 10 000,005 g with an associated expanded uncertainty of 45 mg (coverage factor k=2)

dmD:	Type B rectangular distribution Value: 0 g Halfwidth of Limits: 15·10-3 g

DRIFT OF THE VALUE OF THE STANDARD: The drift of conventional mass of the reference standard is estimated from previous calibrations to be zero within limits ±15 mg

dm:

Type A Method of observation: Indirect SUUS Number of observation: 3 No. Hint Reading Observation 1 Standard 0.010 g     Unknown 0.020 g     Unknown 0.025 g     Standard 0.015 g 0.0100 g 2 Standard 0.025 g     Unknown 0.050 g     Unknown 0.055 g     Standard 0.020 g 0.0300 g 3 Standard 0.025 g     Unknown 0.045 g     Unknown 0.040 g     Standard 0.020 g 0.0200 g Arithmetic Mean: 0.02000 g Pooled Standard Deviation: 25·10-3 g Standard Uncertainty: 0.01420 g Pooled Degrees of Freedom: 50

COMPARATOR / OBSERVATION: A previous evaluation of the repeatability of the mass difference between two weights of same nominal value gives a pooled estimate of standard deviation of 25 mg.

dmC:	Type B rectangular distribution Value: 0 g Halfwidth of Limits: 10·10-3 g

COMPARATOR: No correction are applied for the comparator whereas the uncertainty due to eccentricity and magnetic effects is estimated to have rectangular limits of ±10 mg

dB:	Type B rectangular distribution Value: 0 g Halfwidth of Limits: 10·10-3 g

AIR BUOYANCY: No correction is made for the effects of air boyancy, the limits of deviation are estimated to be ±1.0·10^-6 of the nominal value

Uncertainty Budgets:
m_X: conventional mass of the unknown

Quantity	Value	Standard Uncertainty	Distribution	Sensitivity Coefficient	Uncertainty Contribution	Index
mS	10000.00500 g	0.02250 g	normal	1.0	0.022 g	59.6 %
dmD	0.0 g	8.660·10-3 g	rectangular	1.0	8.7·10-3 g	8.8 %
dm	0.02000 g	0.01420 g	normal	1.0	0.014 g	23.7 %
dmC	0.0 g	5.774·10-3 g	rectangular	1.0	5.8·10-3 g	3.9 %
dB	0.0 g	5.774·10-3 g	rectangular	1.0	5.8·10-3 g	3.9 %
mX	10000.02500 g	0.02915 g

Results:

Quantity	Value	Expanded Uncertainty	Coverage factor	Coverage
mX	10000.025 g	0.058 g	2.00	95% (t-table 95.45%)