Regularly calibrating instruments is necessary in order to reduce measurement errors. It is therefore important to understand how calibration reduces measurement risk, as well as knowing the capabilities of a calibration provider. In the application note, “Eliminate Risk with Proper Calibration,” Keysight Technologies describes measurement risk and its contributing factors. The application note then explains calibration and how it mitigates risk. Different extents of calibration are described as well.
The application note defines measurement risk as the probability of making an incorrect decision. A measurement process has four possible outcomes: Correct pass, correct fail, false pass, and false fail. Measurement risk is directly related to measurement consistency, accuracy, and repeatability. A term used to calculate risk is measurement uncertainty, which takes all the possible errors and combines them to produce a standard deviation. Statistics are then used to calculate risk.
Measurement errors can result from intrinsic, environmental, installation, or operational sources. Intrinsic errors are caused by limitations or inaccuracies of the measurement instrument, while environmental errors are due to the instrument surroundings. Installation errors are a result of connected accessories, such as cables, connectors, probes, and switch boxes. Lastly, operational errors are caused by the engineer or technician operating the equipment.
The application note explains that the intrinsic performance of instruments can change over time. Thus, the uncertainty surrounding performance increases. Increased measurement uncertainty lowers the prospects of achieving consistent, accurate, and repeatable measurements. Proper calibration accurately measures test equipment performance. The document states that the basic definition of calibration is the performance measurement of a test asset based on the international metrology standards.
Different calibration providers offer different coverage scopes. The number of tests and test points indicate the extensiveness of coverage. Providing actual data is essential, as it demonstrates the degree of testing performed. The application note then describes how measurement uncertainty can be determined by various methods. The guardbanding technique, which is used to reduce measurement risk, is mentioned. Lastly, the adjustment-performing capability of a calibration supplier is discussed.
Keysight Technologies, 1400 Fountaingrove Pkwy., Santa Rosa, CA 95403; (800) 829-4444