Language
Country/Area
No result found
The Mystery of Calibration Standards: How to Ensure the Reliability of Measuring Instruments?
In today's measurement technology and metrology fields, the concept of calibration is receiving more and more attention. Calibration, simply put, is comparing the measurements of the device under test to a calibration standard of known accuracy. These standards can be other measuring instruments of known accuracy, devices that generate the data to be measured, or physical artifacts such as long rulers. Comparisons conducted in this way may result in several situations:
No significant error is detected, a significant error is detected but no adjustment is made, or adjustments are made to correct the error to an acceptable level.
According to the definition of the International Bureau of Weights and Measures (BIPM), calibration is an operation that first establishes, under specific conditions, the relationship between the quantitative value provided by a measurement standard and the display of the calibrated instrument; secondly, uses this information to establish from Displays the relationship between the resulting measurement results. This process introduces the concept of measurement uncertainty, establishing an accuracy relationship between the calibration standard and the device under test.
Modern Calibration Process
As the demand for accuracy and uncertainty continues to increase, countries have established national metrology laboratories. In many countries, there are National Metrology Institutes (NMIs) responsible for maintaining the main measurement standards that are used to provide traceability for customers' instruments. These institutions ensure a continuous chain from top standards to measuring instruments. For example, the British NPL, the American NIST, the German PTB, etc.
In the context of the mutual recognition agreement, traceability can now be easily obtained from any participating NMI, and no longer has to obtain it from the NMI of the country where it is located.
Quality of calibration
In order to improve the quality of calibration and have the results accepted by external organizations, calibration and subsequent measurements must be "traceable" to internationally defined units of measurement. Establishing traceability is typically accomplished through formal comparisons to national standards, international standards, or certified reference materials. A quality management system requires an effective metrology system, including formal, regular and documented calibration of all measuring instruments.
Purpose and scope of calibration
The calibration process begins with the design of the measuring instrument, which must be able to "remain calibrated" within its calibration interval. This means that the design must be able to perform measurements "within the engineering tolerance" within a reasonable time under specified environmental conditions. Designs with these characteristics increase the likelihood that the actual measuring instrument will perform as expected.
Manual and automatic calibration
Calibration methods for modern devices can be manual or automated. For example, a manual calibration process for a pressure gauge requires multiple steps to connect the gauge to be measured to a reference master gauge and an adjustable pressure source, and then compare them when pressure is applied. Each step requires manual recording.
Compared with manual pressure calibrators, automatic pressure calibrators combine electronic control units, pressure intensifiers, pressure sensors and data collection facilities to automate data collection.
Historical development
The term "calibration" first appeared during the American Civil War, mainly used to describe the measurement of artillery. In early human civilizations, such as ancient Egypt, Mesopotamia and the Indus River Basin, there were already early measurement and calibration systems. Over time, calibration has gradually evolved into an important technical field to support the development of business and technology.
However, in the face of such a complex calibration process, how can we truly ensure the reliability of each measurement result?
