The sign convention in a calibration table matters. Write the equation before applying any correction to production readings.
A difference and a correction may have opposite signs
A correction compensates for an estimated systematic effect. A table may show indication minus reference, while the correction to add is reference minus indication. Neither heading should be shortened to “difference” in a spreadsheet without preserving its definition.
Check one invented row by hand
At a hypothetical reference of 100.00 g, an instrument indicates 100.20 g. Its indication-minus-reference difference is +0.20 g. In a simple additive model, the correction to add is −0.20 g, giving 100.00 g for that example. Adding +0.20 g would move the reading in the wrong direction.
This invented one-point example does not establish a constant correction over the whole range. A real calibration can require a table, factor or curve, and the uncertainty of the corrected result remains relevant.
Preserve the calculation definition
Keep the certificate column heading, units and interpolation instructions beside the implemented equation. Have a reviewer check a known table row and a second appropriate point. Record whether corrections are applied in the instrument or in later software so that they are not applied twice.
Primary references: JCGM international vocabulary, JCGM international vocabulary.
Measurement review worksheet
This blank worksheet is for your own project. It contains no H M machine trial result.
| Question | Evidence to retain |
|---|---|
| What is the table definition? | Indication−reference or correction-to-add |
| Where is the correction applied? | Instrument or calculation |
| Does the rule vary with range? | Actual table or function |
Customer Questions
Is positive error always a positive correction?
No. Check the certificate’s sign convention.
Can one point justify a constant offset everywhere?
No. The real calibration relationship governs the range.
Can the correction be applied twice?
Yes. Identify instrument-side and software-side transformations.
Primary References
These references support the technical principles discussed in this guide. The worked examples and review questions are educational.
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