Limit Margin & Uncertainty Check
Compute the margin between a measured value and the limit, and check whether it holds after adding expanded uncertainty.
Worked example
Input: Measured level 38 dBµV(/m), Limit 40 dBµV(/m), Expanded uncertainty U 2.8 dB
Result: Margin (limit − measured) 2 dB, Margin including U -0.8 dB, Status (indicative): Below limit, but overlaps the uncertainty band
Result: Margin (limit − measured) 2 dB, Margin including U -0.8 dB, Status (indicative): Below limit, but overlaps the uncertainty band
Formula
Margin = limit − measured value
Margin including uncertainty = limit − (measured value + U)
How it works
Margin is the limit minus the measured value. If the margin including uncertainty is negative, you cannot rule out that the true value exceeds the limit even though the reading is below it. The decision rule (direct comparison or uncertainty-adjusted) follows the applicable standard and your certification body’s policy.
Practical tipCISPR 16-4-2, for example, has the reading compared directly with the limit when the laboratory’s uncertainty is not larger than the reference value set by the standard. Confirm which rule applies before interpreting the indicative status here.
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Results and summaries are for reference. For certification and test reports use the latest official standard text and calibrated instrument data. Last updated: 2026-10-10