Basic Terminology

Sometimes it’s helpful to give definition to some basic terminology used in the calibration game.

Here are a few to get started.

Calibration – the application of a known value (electrical, mechanical, etc.) to a device and the determining that its output accurately represents the applied value. Note: sometimes this definition is modified to include any adjustments necessary to bring a device’s performance into specification.

The definition of a calibrator is corollary, a device of known accuracy that simulates and/or measures a known value (electrical, mechanical, etc.).

Traceability – the prinicple and documentation that allows the tracing of the calibration of a device back to a primary standard maintained by a national standards organization such as the N.I.S.T.

N.I.S.T. is the National Institute of Standards and Technologies (bureau of the U.S. government). This was formerly known as the National Bureau of Standards. It coordinates with other national bodies around the world so that a kilogram is a kilogram worldwide.

Now, here’s a little more detail on some confusing side issues:

Configuration vs. Calibration vs. Verification vs. Confirmation. Due to the lack of a standardized terminology, calibration is often confused with other terms and activities including configuration, verification and confirmation.

Configuration generally means the adjustment of the measurement and / or transmission capabilities of a device to alter its function or use. For example, the measurement range of a thermocouple transmitter may be changed from 0 to 100 degrees Celsius to 0 to 200 degrees Celsius. This would not represent calibration unless a calibration device as defined above was used in the process to determine the accuracy with which it represents this change in its output. The term often applies to the use of a configurator or “electronic screwdriver” to alter the operation of a “smart” transmitter.

Calibration properly refers to the use of an external independent traceable standard to verify that the input to output relationship of the instrument is in specification and to make whatever adjustments may be required to establish that relationship within specification. Note that there is the use of the word verify in this definition.

Confirmation and Verification can be used interchangeably. Again, they refer to the use of an independent standard, but generally do not imply the adjustment part of the calibration definition. The use of these terms is fairly recent.