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42 SMT Magazine • February 2014 summarY: understanding accuracy and re- peatability is an important step to analyze fluid dispensing system performance. But these terms can be prone to misinterpretation when reviewing a product specification. A dispensing motion system can be made to perform better or worse under different op- erating conditions. This article will explain ac- curacy and repeatability, and how they can be applied to different specifications. It will also discuss key considerations when interpreting accuracy and repeatability for decision making. accuracy vs. repeatability "Accuracy" and "repeatability" are com- monly encountered terms used as performance characteristics of fluid dispensing equipment. Unfortunately, these terms are often confused or misunderstood. Accuracy (Figure 1) is a mea- sure of how close an achieved position is to a desired target position. Repeatability (Figure 2) is a measure of a system's consistency to achieve identical results across multiple tests. The ulti- by Nordson aSyMTeK Making Sense of Accuracy, Repeatability and Specification for Automated Fluid Dispensing FEATUrE Figure 1: Accuracy. mate goal is to have both a highly accurate and highly repeatable system. Repeatability is often expressed as the range (variation) of measurements achieved for multi-