As-found vs as-left

As-found readings are taken before any adjustment, cleaning or repair; as-left readings are taken afterwards. A certificate that only reports as-left data tells you the instrument is good now, but nothing about the measurements you made with it since its last calibration.

Why as-found matters

• It is the only evidence of how the instrument performed during the previous interval.
• An out-of-tolerance as-found result triggers an impact assessment on affected measurements, products or decisions.
• As-found history is the basis for setting or adjusting the calibration interval.

Reading the two together

Small drift between calibrations with no adjustment needed supports the current interval. Repeated adjustment at each calibration suggests the interval is too long or the instrument is unsuitable. A large as-found error after a small as-left error at the previous calibration points to an event — damage, misuse, environmental exposure — rather than drift.

In practice

Ask the laboratory to report as-found data even when no adjustment is made (in which case as-found and as-left are the same). Keep both in the instrument record. ValiTrac's calibration data model records both explicitly so that interval and impact decisions can be traced to evidence.