Calibration laboratory personnel often use the terms “in-house calibration” and “internal calibration” interchangeably. Although they sound similar in meaning, these two terms have significantly different applications and using them interchangeably can often create confusion. It can also, unfortunately, lead to deficiencies and issues with earning or maintaining accreditation for your lab.
In many cases, people use both terms to describe where the calibration has taken place. This premise only applies to the term “internal calibration,” which describes a typical calibration performed in your laboratory and is included on your scope of accreditation. On the other hand, the term “in-house calibration” describes a calibration of an A2LA accredited CAB’s own reference measurement standards or measuring and test equipment by the laboratory’s own staff for which the calibration parameters ARE NOT included on their Scope of Accreditation according to P102.
Let’s say, for example, your laboratory is calibrating a feeler gauge using a digital micrometer. The digital micrometer has a direct impact on the calibration of the feeler gauge. If the digital micrometer calibration isn’t included in your scope of accreditation, you must prove traceability with the appropriate in-house calibration documentation. Alternatively, the digital micrometer could be sent to another calibration lab with digital micrometers listed on its scope, potentially saving some time and energy.
There are many reasons a calibration laboratory may not want to include a specific method or piece of equipment on its scope. However, regardless of the reason, if a lab chooses to perform in-house calibrations to satisfy traceability requirements, then they must meet the requirements for doing so.
A2LA’s Traceability Policy
In section T4 of A2LA’s traceability policy, P102, there are detailed requirements for in-house calibrations to be utilized to satisfy traceability requirements. These requirements include, but are not limited to, the records, procedures, and uncertainty budgets necessary to prove traceability. T4 deficiencies are commonly found during assessments, often due to uncertainty budgets lacking all the necessary contributors.
If you’re looking for tools to assist with measurement uncertainty, you can access A2LA’s free measurement uncertainty budget template and the corresponding how-to-use video on our website.
Assessors will check for each requirement using checklist C105, which is also available to A2LA customers. C105 includes the T4 section of P102 and is a simple way to determine whether you have the documentation necessary to prove traceability.
It’s important to know the difference between these two terms so that your organization can earn or maintain its accreditation for the tests and calibrations your scope.
For more information on how to become an accredited testing and calibration lab, visit A2LA.org/Accreditation/Calibration or contact us at Info@A2LA.org.