subject: Defining Calibration and Determining Calibration Intervals [print this page] Defining Calibration and Determining Calibration Intervals
The process of calibration involves comparing a measurement device, also called an unknown, against a standard that is equal or better. Calibrators consider a standard in a measurement to be the reference. In the comparison, the reference is taken to be the more correct of the two. Calibration is performed to determine how far the unknown is from the standard.
A "typical" commercial calibration references a manufacturer's calibration procedure. These types of comparisons are performed with a reference standard at least four times more accurate than the instrument being tested.
Calibrations are essentially insurance policies, and some people think of calibration as a necessary annoyance used to keep auditors off their back. In fact, out of tolerance (OOT) instruments may give false information leading to unreliable products, customer dissatisfaction and increased warranty costs. In addition, OOT conditions may cause good products to fail tests, which ultimately results in unnecessary rework costs and production delays.
How Calibration Intervals are Determined
The instrument "owner" is responsible for determining calibration intervals, based on manufacture recommendations. Commercial calibration laboratories can suggest intervals but in most cases they are not familiar with the details of the instrument's application.
The OEM intervals are typically based on parameters like mean drift rates for the various components within the instrument. However, when determining calibration intervals as an instrument "owner" several other factors should be taken into consideration such as: the required accuracy vs. the instrument's accuracy, the impact an OOT will have on the process, and the performance history of the particular instrument in your application.
Learn more about calibration and calibration intervals.
