The Art of Precision Measurement

Measurement Science is the art of creating and applying instrumentation methods and techniques to extend the range and sensitivity of the human senses. It serves to define and quantify the properties of nature through direct reference to known artifacts and highly reproducible phenomena. Instruments typically cannot provide direct measurement of properties but rather represent them primarily through the established behavior of specially designed devices. For example, the electrical resistivity of pure platinum wire represents the hotness (temperature) of an object with which it is in contact. Direct measurement of true thermodynamic temperature would involve observing a collection of mutually interacting particles and then calculating their average kinetic energy. Instead, the known behavior of Platinum wire is used to represent hotness as the actual direct physical measurement of temperature is impossible. Please go here Resistance Thermometry for a more complete description of how temperature is measured at the highest levels of precision.

The choice of instrument depends upon the type of parameter to be measured and the level of precision dictated by process requirements. Instruments can range from mercury-in-glass to platinum resistance thermometers for measuring temperature; simple rulers to guage block interferometers for measuring length; and digital multimeters to high precision potentiometric bridges for measuring electrical resistance and voltage, just to cite a few examples. Measurement Science always seeks to improve precision and reproducibility while fully characterizing the level of uncertainty inherent to any measurement system.

Understanding the workings of Mother Nature is essential to creating and controlling processes for industrial applications as well as supporting research and development in all areas of Science and Technology. The importance of Measurement Science in everyday life is often overlooked but without it, modern life would be impossible.

The Role of Calibration

Measurement systems need to provide absolute reference to natural physical constants or established artifacts to ensure measured values are "true to nature". Thus, an essential part of any meaurement system is the traceability of its calibration to reference standards. The reference standards themselves form a hierarchy with the highest level being the Primary Standards. These can range anywhere from the macroscopic quantum states exhibited by the Quantized Hall Effect resistance standard to the realization of the triple point of Argon for calibrating Standard Platinum Resistance Thermometers.

National Standards laboratories are the official custodians of the primary reference standards and disseminate their recognized values through direct transfer to user references. Efforts are made to ensure the complete correspondence of all recognized Primary Standards worldwide. In addition, there is ongoing research to create new standards based on fundamental properties of nature or so-called "intrinsic" standards. Many countries have agencies that certify commercial calibration facilities as to the levels of uncertainty and calibration accuracies they can provide. Thus, users can choose the most appropriate level of calibration to suit their requirements and find vendors who can provide traceability accordingly. In addition, there are recognized intervals for recalibrating user standards against primary references to ensure traceability and uncertainty levels are maintained.

The National Institute of Standards and Technolgy (NIST) is responsible for creating and maintaining Primary Reference Standards in the United States. Detailed information on the services provided and ongoing research can be found here: http://www.nist.gov/index.html.

For more information about determining the levels of calibration you may require and simple ways to ensure the basic accuracy of your measurement systems please fell free to contact Zero K Designs.