The challenge: expecting a repair from a calibration
An instrument can operate normally while having a measurement error that matters to a particular process. It can also be calibrated without being changed. Before ordering work, define what you need to learn and whether any adjustment is authorised.
What each activity does
Calibration relates instrument indications to reference values with consideration of measurement uncertainty. Adjustment changes the measuring system to provide the intended indications. Verification establishes whether specified requirements are met. These distinctions follow the VIM vocabulary: calibration is not the same activity as adjustment or verification. See the linked BIPM definitions below.
Testing is a broader word. It may mean a visual inspection, an operating check or evaluation against a criterion. Its scope and acceptance conditions need to be stated.
A useful work sequence
- Define the application, operating range and environment.
- Identify the instrument, probe and accessories included in the work.
- Record the condition found before any agreed adjustment.
- Evaluate the results against the intended use and the agreed decision rule where a conformity statement is required.
- If adjustment is needed, establish who may perform it and what measurements must follow.
For example, a process with a narrow measurement requirement cannot rely on the words “calibrated instrument” alone. The result, conditions and uncertainty must be considered alongside the requirement. A certificate supports that decision; its mere existence does not make the decision.
Common mistakes
Adjusting first can remove evidence needed to assess earlier measurements. Choosing a convenient test point outside the working range can leave the actual application unresolved. Comparing two displays does not necessarily provide a suitable reference when the quality of the second instrument is unknown.
Before contacting the laboratory
Prepare the instrument and probe identification, operating range, previous certificate and applicable specification. State whether records before and after adjustment are required. Include the cables, display and accessories used in practice, and agree the treatment of any nonconforming result.
Frequently asked questions
Does new equipment need assessment? New equipment still needs documents and suitability appropriate to its intended use. The decision depends on the equipment and quality system.
Does calibration always include adjustment? No. Calibration may document the instrument without changing it.
Contact ENDI Laboratory to define the work around your equipment and application.
