> For the complete documentation index, see [llms.txt](https://help.boomerang3.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://help.boomerang3.com/boomerang-3-calibration-app-manual/advanced/calculation-method/uncertainty.md).

# Uncertainty

<table><thead><tr><th width="86">ui</th><th width="300">Uncertainty sources</th><th width="119">Distribution</th><th>Formula in squared</th></tr></thead><tbody><tr><td> </td><td><strong>Basic uncertainties</strong></td><td> </td><td> </td></tr><tr><td>1</td><td>Reference sensor uncertainty taken from its calibration certificate</td><td>Normal</td><td>(x/2)^2</td></tr><tr><td>2</td><td>Reference sensor long time drift after calibration</td><td>Rectangle</td><td>(x/SQRT(3))^2</td></tr><tr><td>3</td><td>Reference sensor resolution and reading error</td><td>Rectangle</td><td>(x/SQRT(3))^2</td></tr><tr><td>4</td><td>Hysteresis</td><td>Rectangle</td><td>(x/SQRT(3))^2</td></tr><tr><td>5</td><td>Cal sensor resolution and reading error</td><td>Rectangle</td><td>(x/SQRT(3))^2</td></tr><tr><td>6</td><td>Drift of ref sensor readings</td><td>Variation width</td><td></td></tr><tr><td>7</td><td>Drift of cal sensor readings</td><td>Variation width</td><td></td></tr><tr><td> 6 or 7</td><td>Max drift from 2 values above</td><td>Variation width</td><td>(MAX([6],[7])/(2*SQRT(3)))^2</td></tr><tr><td> </td><td><strong>Other uncertainties</strong></td><td> </td><td> </td></tr><tr><td>8a</td><td>Temp drift reference sensor, ± x ° C</td><td>Rectangle</td><td>(x/SQRT(3))^2</td></tr><tr><td>8b</td><td>Temp drift measuring object, ± x ° C</td><td>Rectangle</td><td>(x/SQRT(3))^2</td></tr><tr><td>8c</td><td>Repeatability</td><td>Rectangle</td><td>(x/SQRT(3))^2</td></tr><tr><td>9</td><td>Uncertainty ui</td><td> <mark style="background-color:green;">ui</mark> = SQRT of sum</td><td>Sum of squared column</td></tr></tbody></table>

Total measurement uncertainty (k=2) is calculated as 2\*ui and rounded to 2 digits after coma.

If the result is smaller than 0.2 then 0.2 is reported on the certificate.


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