Calibration of a nominal 10 kOhm standard resistor
The resistance of a four terminal standard resistor is determined by direct substitution using a long scale digital multimeter (7½digit DMM) on its resistance range, and a calibrated four terminal standard resistor of the same nominal value as the item to be calibrated as reference standard. The resistors are immersed in a well stirred oil bath operating at a temperature of 23 °C monitored by a centrally placed mercuryinglass thermometer.The resistors are allowed to stabilise before the measurement. The four terminal connectors of each resistor are connected in turn to the terminals of the DMM. It is determined that the measuring current on the 10 kOhm range of the DMM of 100 µA is sufficiently low not to cause any appreciable selfheating of the resistors. The measuring procedure used also ensures that the effects of external leakage resistances on the result of measurement can be considered to be insignificant.
Model Equation:
R_{X} = ( R_{S} + δR_{D} + δR_{TS} ) × r_{C} × r  δR_{TX}

List of Quantities:
Quantity  Unit  Definition 

R_{X}  Ω  resistance of the unknown resistor 
R_{S}  Ω  resistance of the reference 
δR_{D}  Ω  change of the resistance of the reference since its last calibration due to drift 
δR_{TS}  Ω  temperature related resistance deviation of the reference 
r_{C}  correction factor for parasitic voltages and instrument resolution  
r  =R_{iX}/R_{iS} ratio of the indicated resistance for the unknown resistor and the reference resistor  
δR_{TX}  Ω  temperaturerelated resistance deviation of the unknown resistor 
R_{S}: 
Type B normal distribution Value: 10000.053 Ω Expanded Uncertainty: 5·10^{3} Ω Coverage Factor: 2 
δR_{D}: 
Type B rectangular distribution Value: +20·10^{3} Ω Halfwidth of Limits: 10·10^{3} Ω 
δR_{TS}: 
Type B rectangular distribution Value: 0 Ω Halfwidth of Limits: 2.75·10^{3} Ω 
r_{C}: 
Type B triangular distribution Value: 1.0 Halfwidth of Limits: 1.0·10^{6} 
r: 
Type A Method of observation: Direct Number of observation: 5
Arithmetic Mean: 1.0000105000 
δR_{TX}: 
Type B rectangular distribution Value: 0 Ω Halfwidth of Limits: 5.5·10^{3} Ω 
Uncertainty Budgets:
R_{X}: resistance of the unknown resistorQuantity  Value 
Standard Uncertainty 
Distribution 
Sensitivity Coefficient 
Uncertainty Contribution 
Index 

R_{S}  10000.05300 Ω  2.50·10^{3} Ω  normal  1.0  2.5·10^{3} Ω  9.0 % 
δR_{D}  0.02000 Ω  5.77·10^{3} Ω  rectangular  1.0  5.8·10^{3} Ω  48.1 % 
δR_{TS}  0.0 Ω  1.59·10^{3} Ω  rectangular  1.0  1.6·10^{3} Ω  3.6 % 
r_{C}  1.000000000  408·10^{9}  triangular  10000  4.1·10^{3} Ω  24.0 % 
r  1.0000105000  70.7·10^{9}  normal  10000  710·10^{6} Ω  0.7 % 
δR_{TX}  0.0 Ω  3.18·10^{3} Ω  rectangular  1.0  3.2·10^{3} Ω  14.5 % 
R_{X}  10000.17800 Ω  8.33·10^{3} Ω 
Results:
Quantity  Value 
Expanded Uncertainty 
Coverage factor 
Coverage 

R_{X}  10000.178 Ω  0.017 Ω  2.00  95% (ttable 95.45%) 