Standards basis
MeterProof is framed around ISO 5168:2005 for uncertainty combination, with sensitivity relationships drawn from ISO 5167 where appropriate, and GUM-style treatment of Type A and Type B contributions.
Type A and Type B inputs
Where repeated observations or sample data exist, Type A treatment may be appropriate. Where uncertainty is based on specifications, calibration information, bounded assumptions, or engineering judgement, Type B treatment is generally more appropriate.
Sensitivity coefficients
The uncertainty budget is not just a list of percentages. Each contributor is weighted through its sensitivity coefficient so the result reflects its effect on the final measured quantity.
Effective degrees of freedom and k factor
Where Type A data materially influences the combined standard uncertainty, the effective degrees of freedom can affect the expansion factor. That is why the reported k value is not always exactly 2.000.
What the result does and does not mean
The report shows the consequence of the basis provided. It does not prove that every input is correct or that every assumption is universally valid. Good input selection and independent engineering judgement still matter.