The defined acceptance limits and rules used to determine whether an instrument meets its required specifications during calibration, resulting in a pass (in tolerance) or fail (out of tolerance) determination.
Pass/fail criteria establish the boundaries for declaring whether an instrument conforms to its specifications. These criteria typically consist of the tolerance limits for each measurement parameter and the decision rule that defines how measurement uncertainty is considered in the determination. The criteria must be clearly defined in the calibration procedure before calibration begins.
The simplest approach uses the manufacturer's specified tolerance as the pass/fail boundary, without accounting for measurement uncertainty (simple acceptance). More rigorous approaches incorporate decision rules that consider measurement uncertainty, such as guard-banding (narrowing acceptance limits to control false accept risk) or the approach specified in ANSI/NCSL Z540.3 (limiting the probability of false accept to 2% per tolerance limit).
For calibration management, pass/fail criteria must be documented, traceable to requirements, and consistently applied. The criteria may come from multiple sources: manufacturer specifications, industry standards, customer requirements, or engineering specifications. When multiple sources exist, the most stringent criteria typically apply. Calibration software should enforce the correct criteria for each instrument type and automatically flag results that fall outside the acceptance limits. Clear documentation of pass/fail criteria on calibration certificates provides transparency to the customer and supports audit compliance.
In aerospace calibration labs, pass/fail criteria for torque wrenches might specify ±4% accuracy per AS9100 requirements. A 100 ft-lb wrench reading 96.5 ft-lb would pass, but 95.8 ft-lb would fail and require adjustment or removal from service. Medical device manufacturers face stricter criteria - a digital pressure gauge used in ventilator testing might require ±0.25% accuracy per FDA 21 CFR 820.72. If the gauge reads 101.3 kPa when the standard applies 100.0 kPa, it exceeds the ±0.25 kPa tolerance and fails calibration. Common audit findings occur when labs use inappropriate guard bands or apply test uncertainty ratios (TUR) incorrectly. A defense contractor failed an AS9110 audit when their multimeter calibrations used 3:1 TUR instead of the required 4:1 ratio for critical measurements. Another manufacturer received a 483 observation when their temperature chamber pass/fail criteria didn't account for measurement uncertainty, leading to false accepts where instruments appeared to pass but were actually borderline failures when uncertainty was properly considered.
ISO/IEC 17025:2017 Section 7.8.6.1 requires laboratories to record calibration results and determine conformity to specifications. AS9100D Section 7.1.5 mandates measurement traceability with defined acceptance criteria. ISO 13485:2016 Section 7.6 requires measuring equipment to meet specified requirements before use. ANSI/NCSL Z540.3-2006 Section 4.3 details decision rules for conformity assessment, including guard bands and test uncertainty ratios. GUM (Guide 98-3) provides the framework for uncertainty evaluation that underpins pass/fail decisions. Auditors specifically examine decision rules documentation, verify appropriate TUR calculations (typically 4:1 for critical applications), and ensure guard bands are properly applied. They look for evidence that measurement uncertainty is considered in conformity statements per ISO/IEC 17025 Section 7.8.6.2, and that non-conforming instruments are properly identified and controlled per the applicable quality standard's requirements for measuring equipment control.
CalibrationOS implements pass/fail criteria through its Standards Management module, where users define tolerance limits, test uncertainty ratios, and guard bands for each instrument type. The Calibration Execution module automatically evaluates measured values against these criteria, applying proper uncertainty calculations and decision rules per ANSI/NCSL Z540.3 requirements. Real-time pass/fail indicators guide technicians during calibration procedures, while the system captures all relevant data including as-found/as-left conditions and uncertainty contributions. Certificate generation automatically includes conformity statements with proper decision rule documentation. The Audit Trail feature maintains complete records of pass/fail determinations with timestamps and user identification, ensuring compliance with ISO/IEC 17025 requirements. Dashboard analytics track pass/fail rates and trends, helping quality managers identify systematic issues before they impact production or regulatory compliance.
Pass/fail criteria are derived from manufacturer specifications, industry standards, or customer requirements. They define the tolerance limits and decision rules (including whether measurement uncertainty is accounted for) that determine conformity.
Yes. Modern standards (ISO 17025, ANSI/NCSL Z540.3) require that measurement uncertainty be considered when making conformity statements. This is implemented through decision rules, often using guard-banding to control false accept risk.
This article is licensed CC BY-SA 4.0. Share, adapt, and reuse with attribution to calibrationos.com/glossary/pass-fail-criteria.
Industry benchmarks, best practices, and calibration tips — delivered to your inbox.
Free calibration management software with audit-ready tracking, uncertainty budgets, and compliance tools.
Start Free — No Credit Card