Category Archives: News and Events

Inside Story Issue 1

The Interface Assessment Division, a unit of the Naval Surface Warfare Center (NSWC) located in Corona, California, uses its precision measurement capabilities (traceable to national standards) to assure the form, fit, and functional requirements of physical interchangeability and mechanical interoperability as specified by the Navy.

Performance of CMMs: Testing, Calibration, and Uncertainty

[embedit snippet="2-columns"] 1. Introduction Coordinate measuring machines (CMMs) are the most advanced dimensional measuring instruments on the market today. Their unlimited versatility allows them to be used for an infinite number of measurements. But the inherent flexibility of CMMs can also make them difficult to implement. If you are new to CMMs, you are probably wondering how to determine which of the many available machines will be accurate enough for your needs and also how to best compare two similar looking machines. Once a CMM is installed, the question of how to calibrate a machine with so many capabilities is often asked. And now, with many new quality initiatives being pushed onto manufacturing and calibration, the big question is how to estimate the uncertainty of measurements being made using CMMs. We will try to answer all these questions...

On Measurement Uncertainty

The concept of measurement uncertainty is continuing to create confusion in the dimensional metrology community. As a supplier of measuring instruments and tools, Mitutoyo America receives many questions from customers about measurement uncertainty. I hope the answers to the questions below, along with the included example, will help reduce some confusion. -JGS What is measurement uncertainty? Measurement uncertainty is the estimation of potential errors in a measurement process. When determining uncertainty, you must consider all factors that impact the variation in your measurement results. Error in the measuring instrument, tool, or gage is just one source of uncertainty. Another contributor is the environment, particularly temperature for dimensional measurements. Other common factors to consider are calibration limits, operators, repeatability, and the geometry and condition of the measured workpiece. How is uncertainty expressed? Say you use an external micrometer to measure...

On Accreditation and Calibration

Over the past few years a number of new quality requirements have been released that have created some confusion in the dimensional metrology community. I have been asked many of the following questions, and I hope that these answers are useful to you and your organization. -JGS What is accreditation? Accreditation is the process of proving competency of calibration and testing services. In addition to management and quality systems requirements, accreditation demands proof of the technical ability of the calibration provider. The measurement capability of the calibration service is quantified using measurement uncertainty, which is a key requirement in accreditation. Accreditation also verifies that calibration procedures are appropriate and valid. Accreditation is therefore critical to ensuring traceability of measurements. What is measurement uncertainty? Measurement uncertainty is an estimation of potential errors in a particular measurement process. Uncertainty...