SAC-SINGLAS accreditation under ISO/IEC 17025:2017 is Singapore's highest recognition of a calibration laboratory's technical competence — and it is increasingly required by Singapore's pharmaceutical, aerospace, electronics, and utilities sectors as a condition of supplier approval. An SAC assessment visit typically runs 1–3 days depending on laboratory scope, with a lead assessor and one or more technical assessors reviewing both management system documentation and technical performance. This guide is for calibration laboratory managers preparing for their first accreditation, reassessment, or extension-of-scope audit.
Understanding the ISO/IEC 17025:2017 Structure
The standard has five main sections: General Requirements (impartiality and confidentiality), Structural Requirements (legal entity, management structure, scope definition), Resource Requirements (personnel, facilities, equipment, external services), Process Requirements (the actual calibration work), and Management System Requirements (choosing Option A documentation system or Option B ISO 9001 integration).
SAC assessors will review evidence for all five areas. Prepare documentation mapped explicitly to these clause numbers — assessors work through the standard clause by clause and your evidence must be findable and traceable.
Documentation Preparation
Quality Manual and Policies
Your Quality Manual must address all ISO/IEC 17025 requirements and describe the laboratory's scope (parameters, measurement ranges, and methods). The scope must match the application submitted to SAC — assessors verify that your documented scope matches what you actually calibrate and what you applied for. Ensure the Quality Manual version and approval date are current (within the last 3 years at minimum, reflecting any standard or procedure changes).
Calibration Method Procedures
For each parameter and range in your scope, you need a validated calibration procedure documenting: applicable international/national standard (e.g., IEC 60068-1 for environmental testing, OIML R111 for mass standards), equipment required, environmental conditions required, step-by-step calibration process, measurement uncertainty evaluation method, and acceptance/rejection criteria. For test methods published by recognised standards bodies (e.g., Fluke calibration procedure for Fluke 435-II), you may use the published method with a brief laboratory validation record.
Measurement Uncertainty Budgets
Every calibration in your scope must have a documented measurement uncertainty evaluation — the uncertainty budget. The budget identifies all sources of uncertainty (reference standard uncertainty, environmental effects, instrument resolution, repeatability, operator effects), quantifies each as a standard uncertainty, combines them as root-sum-of-squares (for uncorrelated sources), and multiplies by the coverage factor (k=2 for 95% confidence) to give expanded uncertainty U. If your uncertainty budgets have not been reviewed since the previous assessment, update them to reflect any new reference standards, changed procedures, or new measurement ranges.
Equipment and Reference Standards
Calibration Status of Reference Standards
Every reference standard used in your calibration work must have a current calibration certificate traceable to national standards (A*STAR National Metrology Centre or equivalent ILAC MRA-signatory laboratory). Prepare a master equipment list listing each reference standard's model, serial number, calibration certificate number, calibration date, and next calibration due date. During the audit, assessors will select a sample of instruments from this list and verify their certificates physically or in your document system.
Calibration Intervals
Demonstrate that your calibration interval policy is risk-based — the interval assigned to each instrument reflects its stability history, usage, and the criticality of the measurement. For a primary electrical reference (e.g., Fluke 5500A multi-product calibrator), a 12-month interval is standard. For stable mass standards in controlled environments, 3–5 year intervals may be defensible with stability data. Document your justification for each interval assignment.
In-Service Checks
Between formal calibrations, reference standards should have documented in-service checks verifying they remain within specification. This may be a check against a redundant reference, an internal quality control chart, or a published stability specification. Assessors look for evidence that the laboratory monitors its reference standard performance between calibrations — not just at calibration time.
Personnel Competency Records
ISO/IEC 17025 requires that laboratory personnel performing calibrations are competent — qualified by education, training, and experience. Prepare personnel files for each calibration technician showing: educational qualifications, technical training records (courses attended, internal training records), records of supervised calibrations, and documented authorisation for each calibration activity they are approved to perform independently. The authorisation record (signed by the laboratory manager or technical manager) demonstrates controlled competency management.
Proficiency Testing (PT) Participation
SAC requires SINGLAS-accredited laboratories to participate in proficiency testing programmes appropriate to their scope. For Singapore laboratories, relevant PT providers include SPRING Singapore's National Metrology Centre PT programmes, APMP (Asia Pacific Metrology Programme) bilateral comparisons, and NATA/UKAS-organised PT rounds. Prepare records of PT participation for the last 3 years, including the PT report, your result (z-score or En number), and any corrective actions taken for unsatisfactory results. PT participation is typically 1–2 exercises per parameter per 3-year accreditation cycle.
Environmental Conditions Monitoring
Calibration laboratories must monitor and record environmental conditions (temperature, humidity) during calibrations where these affect measurement quality. Prepare calibration records showing the temperature and humidity logged at the time of each calibration, and verify that your environmental records are linked to your calibration records — assessors check that conditions were within specification during each calibration activity. Rotronic data loggers with continuous logging, calibration certificates, and data export capability are the standard choice for Singapore calibration laboratory environmental monitoring.