Decision rules & conformity
How Open Gauge decides pass/fail once measurement uncertainty is in the picture — simple acceptance, guard-banding, and shared risk.
ISO/IEC 17025 §7.1.3 and §7.8.6 require that whenever a lab issues a pass/fail statement, it documents which decision rule was applied — a bare "reading within spec" comparison isn't sufficient once measurement uncertainty is accounted for. Open Gauge stores the decision rule and the resulting conformity statement on every calibration.
The three rules
Let be the calibration's max error and be the channel's accuracy spec (e.g. ±0.5 °C, or ±1% FS converted to an absolute value), and be the expanded uncertainty.
| Rule | Passes when | Effect | When to use |
|---|---|---|---|
| Simple acceptance (default) | Ignores uncertainty entirely. | No formal risk analysis done yet, or the customer hasn't agreed to a different rule. | |
| Guard band | The acceptance zone shrinks inward by . | Reduces false-accept risk — use when a false pass is costly. | |
| Shared risk | The acceptance zone expands outward by . | Reduces false-reject risk, at the cost of some false-accept risk near the boundary — use when a false fail is costly. |
Notice these three rules can genuinely disagree on the same fit and the same spec — see Example 1.3 for a worked case where all three rules produce a different verdict from identical input data.
What gets stored
Every calibration stores a conformity_statement carrying the full record: the decision rule
used, a human-readable rendering of the specification (e.g. "±0.5% of full scale"), the
expanded uncertainty applied (if any), whether it passed, and a reason (populated only when no
accuracy spec was configured at all, meaning conformity wasn't evaluated).
Saving a non-conforming calibration
Saving is never blocked by a non-conforming result. A failed calibration is itself an important record — Open Gauge's calibration philosophy treats history as immutable and never suppresses a real result just because it's inconvenient. When a result doesn't conform, the save-confirmation dialog names the specification and decision rule explicitly, and the save button relabels to "Save anyway."
No standalone tolerance preview
There's no separate client-side "what if" tolerance field — an earlier version of the wizard had one, disconnected from the channel's real spec and never persisted, which could contradict the actual saved conformity result. The conformity statement shown in the wizard's uncertainty panel is the one that gets saved and printed on the certificate.