TABLE OF CONTENTS The overall accuracy of a measurement system depends on the accuracy of the system's individual components, the accuracy of the standards used in calibration, the factors that affect the accuracy of the components and standards, and even the actions of the person making the measurement.
We discussed the accuracy of the individual components in chapter 2, section 2.6, "Accuracy," and the factors that affect the accuracy in section 2.8, "Environmental Effects on Transducer Characteristics." A detailed analysis of how to deal with these factors is given in chapter 19. The accuracy of components or systems is always judged in relation to some known reference or standard. This standard has some stated accuracy that must be included in the overall accuracy of the component or system. In some measurement situations, the equipment operator can influence the value of the measurement. This can happen when a person views a dial indicator from an angle that causes an error in the reading (parallax error). It can also happen when a person views a rapidly changing digital display and mentally averages the readings to arrive at a single measurement. Another person making the same observations may come to a different result. These actions are called operator errors, and they should be included in the overall determination of accuracy if they can be estimated or quantified.
The methods used to combine several different sources of error or accuracy into a single accuracy figure are based on some applications of statistics. These applications have been...
