The operation of bringing a measuring instrument into a state of performance suitable for its use, typically by correcting bias, zero offset, or span errors identified during calibration.
Adjustment is the act of modifying an instrument to correct errors found during calibration. This may involve zeroing the instrument, adjusting a potentiometer, applying an offset correction, changing a gain setting, or performing a multi-point linearization. The goal is to bring the instrument's readings as close to the true values as possible across its operating range.
It is important to distinguish between calibration and adjustment. Calibration is the process of comparing an instrument against a reference standard and documenting the results. Adjustment is a separate action that changes the instrument's response. Not every calibration requires an adjustment — if the as-found readings are within tolerance, the instrument is returned to service without modification. Adjustment is only performed when the as-found readings show unacceptable error.
In calibration management, the sequence of recording as-found data before any adjustment and as-left data after adjustment is critical. The as-found data reveals the instrument's condition as it was being used, enabling assessment of the validity of measurements made since the last calibration. The as-left data confirms the instrument's condition as it is returned to service. ISO 17025 and most quality systems require this documentation to maintain traceability and support nonconformance investigations.
Calibration is the process of comparing an instrument to a reference standard and documenting the errors. Adjustment is the separate act of modifying the instrument to reduce those errors. Calibration may or may not include adjustment.
An instrument should be adjusted when its as-found readings fall outside the specified tolerance. If readings are within tolerance, no adjustment is needed. As-found data must always be recorded before any adjustment is made.
Free calibration management software with audit-ready tracking, uncertainty budgets, and compliance tools.
Get Started Free