Calibration is essential in almost every facet of industrial processes today. The calibration process verifies test instrument accuracy by comparison with recognized standards, and measurement validity hinges on one crucial concept: traceability. Traceability adherence ensures a continuous link between your unit under test (UUT) and that standard. In this blog post, we examine traceability, exploring why it is necessary for achieving accurate measurement results.

WHAT IS TRACEABILITY

Traceability is documented evidence that confirms measurement accuracy through an unbroken chain of calibration events. When calibrating an instrument, accurate measurement results rely on this definitive link between the UUT’s indication and those established standards. For most industrial customers, an accredited calibration laboratory typically maintains these reference standards, possibly even climbing all the way to the National Institute of Standards and Technology (NIST). The accredited lab uses its standards, which are traceable to a higher-echelon lab, to calibrate field-level instruments. This traceable path ensures the calibrated instrument measurements are dependable.

WHY TRACEABILITY MATTERS 

1. QUALITY ASSURANCE AND COMPLIANCE

Most industries perform some sort of measurement(s) to ensure product quality. This could be product sampling at various stages in the production process or end-of-line verification of the finished product. Quality assurance personnel rely on the traceability of their instruments to provide valid measurements, thus verifying in-specification results. The instruments used should be traceable to a higher-level standard, most often provided through a calibration service, either internal or external to the company. This traceability is critical in meeting regulatory requirements/standards, i.e., ISO standards or FDA regulations, as part of overall confirmation that the product meets specifications. Ensuring proper traceability demonstrates a commitment to compliance and overall product quality.

2. MEASUREMENT CONFIDENCE

Traceable measurements provide a higher confidence level and produce more consistent results. Users can trust that their data is reliable, thereby ensuring their product(s) meet specified tolerances. Proper traceability through established higher-level calibration standards will inherently result in nearly identical (nothing is ever perfect) results across different tools, laboratories, and even geographic locations. Traceability is a key factor in making informed decisions regarding production activities to ensure your company can achieve the best results.

3. LEGAL AND FINANCIAL IMPLICATIONS 

A transparent audit trail can protect businesses from legal liability and regulatory issues. Proper traceability documentation provides objective evidence to any auditor that your program complies with regulatory or other requirements, thus reducing the risk of legal penalties and product recalls. Additionally, proper traceability mitigates risk, helping defend against financial audits, investigations, and other compliance-related actions. The same evidence of your commitment to compliance and quality mentioned above helps to safeguard against legal and economic setbacks

4. PROBLEM RESOLUTION

Another benefit of proper traceability is identifying and rectifying issues. Sound data provides the basis to delve into any measurement or calibration issue as it happens and pinpoint the concern to a product or process, taking swift action to resolve it. The confidence provided by traceability facilitates effective problem-solving strategies and prevents recurring issues. As a result, it reduces downtime and associated costs while enhancing product quality. Traceability ensures confidence in decisions and allows for continuous improvement.

THE IMPORTANCE OF AN UNBROKEN CHAIN OF COMPARISONS

Traceability links the measurement to an internationally recognized standard through a documented series of comparisons. This “unbroken chain” ensures the integrity of measurement data, beginning with an initial comparison to the primary standard and then passing through one or more secondary standards to a working standard on the production floor.

Each step must be properly documented, ensuring each comparison is traceable to the reference standard. This unbroken chain of comparisons ensures reliability and accuracy at each step, with the ultimate PASS or FAIL result completely dependent upon the chain and proper documentation. Any flaw in the process could introduce errors that would affect down-the-line measurements, ultimately impacting quality control, compliance, and product reliability.

Figure 1: Calibration hierarchy from primary standard to test equipment

From 4.1 Traceability: An Unbroken Chain of Transfer Comparisons, by Gigahertz-Optik, n.d. (https://www.gigahertz-optik.com/en-us/service-and-support/knowledge-base/basics-light-measurement/detector-calib/traceability/). CC-BY 2.0.  

Figure 2: Hierarchy of standards

From 4.1 Traceability: An Unbroken Chain of Transfer Comparisons, by Gigahertz-Optik, n.d. (https://www.gigahertz-optik.com/en-us/service-and-support/knowledge-base/basics-light-measurement/detector-calib/traceability/). CC-BY 2.0.

IMPLEMENTING TRACEABILITY IN CALIBRATION