Establish a baseline on an independent check standard immediately after a valid calibration. Choose a standard that is stable and sensitive to the error modes that matter, then compare complex data or bounded metrics against documented warning and failure limits. The check standard must not be the same artifact used to create the calibration being verified.
Set a maximum elapsed-time interval, but also trigger verification after cable movement or flexure, connector remating, switch-path change, fixture reload, probe maintenance, overload, impact, temperature excursion, failed gauge or suspicious correlation. High-use production paths usually need event and cycle controls in addition to a calendar interval.
When verification fails, quarantine the path, identify the last successful check, inspect hardware and recalibrate or repair as needed. Assess DUT results produced since the last known valid state. Trend the verification record so the interval can be tightened or relaxed from evidence rather than habit.