{"id":4884,"date":"2020-04-28T14:53:15","date_gmt":"2020-04-28T14:53:15","guid":{"rendered":"https:\/\/www.srpcontrol.com\/?p=4884"},"modified":"2023-09-21T18:44:59","modified_gmt":"2023-09-21T18:44:59","slug":"understanding-as-found-and-as-left-data-when-it-comes-to-calibration","status":"publish","type":"post","link":"https:\/\/www.srpcontrol.com\/understanding-as-found-and-as-left-data-when-it-comes-to-calibration\/","title":{"rendered":"Understanding As-Found and As-Left Data When It Comes to Calibration"},"content":{"rendered":"

Have you sent your instrument out for recalibration, gotten the certificate back, and seen “As-Found Calibration” or “As-Left Calibration” and wondered what this means? Here is a guide to understanding what these terms mean.<\/span><\/p>\n

The Definition of Calibration<\/span><\/strong><\/p>\n

Calibration compares a measurement device (an unknown) against an equal or better standard.\u00a0<\/span><\/p>\n

A standard in a measurement is considered the reference. It is the one in the comparison taken to be the more correct. Calibration finds out how far the unknown is from the standard.<\/span><\/p>\n

A typical commercial calibration uses the manufacturer’s calibration procedure. It is performed with a reference standard at least four times more accurately than the instrument under test.<\/span><\/p>\n

What As-Found Calibration Means<\/span><\/strong><\/p>\n

As-Found data is what a calibration lab finds when it calibrates on an as-received device, like a calibrator, gauge, or sensor, before any adjustments or repairs.<\/span><\/p>\n

What As-Left Calibration Means<\/span><\/strong><\/p>\n

As-Left data is the calibration data when the instrument leaves the lab.<\/span><\/p>\n

As-Found and As-Left Data Importance\u00a0<\/span><\/strong><\/p>\n

Suppose the As-Found data is outside of published specifications. In that case, the device must be adjusted to bring it within spec. For example, the data will sometimes be linearized if this process consists of zero, offset, and span adjustments. Sometimes limits narrower than the published specs are applied to account for uncertainties in the measuring system, known as guard banding. Another possibility is that the device needs repairing. No matter the situation, the calibration is re-run. The data generated during this recalibration is the as-left data.<\/span><\/p>\n

As-Found data is crucial because it will determine the validity of any tests run with the device in the past. In addition, as-Found data provides a history of the sensor’s drift characteristics over time. It also indicates how often the sensor should be calibrated and if it meets the manufacturer’s recommended calibration interval specification.<\/span><\/p>\n

As-Left data is also essential because it assures the operator that future tests using the device conform to expectations of inaccuracy.<\/span><\/p>\n

Calibration Certificates Terms<\/span><\/strong><\/p>\n