For a device calibration to be valid, the instruments used to calibrate the device must have a ______?

• A. certificate of calibration
• B. calibration procedure
• C. traceable standard
• D. calibration sticker

Answer: (A)

The key idea is that calibration validity depends on having a documented, verified status for the instrument used to calibrate other equipment. A certificate of calibration provides that formal record: it traces the instrument’s own calibration back to recognized standards, lists the results and the associated measurement uncertainty, notes the calibration date, and states when the next check is due. This documentation proves the instrument is within spec at the time of calibration and that its measurements can be trusted for calibrating other devices. Without this certificate, there’s no verifiable proof of the instrument’s accuracy or its traceability, so the calibration of the device under test isn’t considered valid.

A calibration procedure describes how to perform calibration but not whether the instrument being used is itself calibrated. A traceable standard is the reference used during calibration, but the certificate is the record that confirms the instrument has been calibrated to that standard. A calibration sticker is merely a label and doesn’t provide documented evidence of accuracy or traceability.