A measurement systems analysis (MSA) is a thorough assessment of a measurement process, and typically includes a specially designed
experiment that seeks to identify the components of variation in that measurement process. Just as processes that produce a product may vary, the process of obtaining measurements and data may also have variation and produce incorrect results. A measurement systems analysis evaluates the
test method,
measuring instruments, and the entire process of obtaining measurements to ensure the integrity of data used for analysis (usually quality analysis) and to understand the implications of measurement error for decisions made about a product or process. Proper measurement system analysis is critical for producing a consistent product in manufacturing and when left uncontrolled can result in a drift of key parameters and unusable final products.
MSA is also an important element of
Six Sigma methodology and of other
quality management system
A quality management system (QMS) is a collection of business processes focused on consistently meeting customer requirements and enhancing their satisfaction. It is aligned with an organization's purpose and strategic direction (ISO 9001:2015). I ...
s. MSA analyzes the collection of equipment, operations, procedures, software and personnel that affects the assignment of a number to a measurement characteristic.
A measurement systems analysis considers the following:
* Selecting the correct measurement and approach
* Assessing the measuring device
* Assessing procedures and operators
* Assessing any measurement interactions
* Calculating the
measurement uncertainty
In metrology, measurement uncertainty is the expression of the statistical dispersion of the values attributed to a measured quantity. All measurements are subject to uncertainty and a measurement result is complete only when it is accompanied by ...
of individual measurement devices and/or measurement systems
Common tools and techniques of measurement systems analysis include: calibration studies, fixed effect ANOVA, components of variance, attribute gage study, gage R&R,
ANOVA gage R&R, and destructive testing analysis.
The tool selected is usually determined by characteristics of the measurement system itself.
An introduction to MSA can be found in chapter 8 of Doug Montgomery's Quality Control book.
These tools and techniques are also described in the books by Donald Wheeler
and Kim Niles.
Advanced procedures for designing MSA studies can be found in Burdick ''et al.''
Equipment: measuring instrument,
calibration, fixturing.
* People: operators, training, education, skill, care.
* Process: test method,
specification.
* Samples: materials, items to be tested (sometimes called "parts"),
sampling plan
In statistics, quality assurance, and survey methodology, sampling is the selection of a subset (a statistical sample) of individuals from within a statistical population to estimate characteristics of the whole population. Statisticians attempt ...
, sample preparation.
* Environment:
temperature,
humidity, conditioning,
pre-conditioning.
* Management: training programs,
metrology
Metrology is the scientific study of measurement. It establishes a common understanding of units, crucial in linking human activities. Modern metrology has its roots in the French Revolution's political motivation to standardise units in Fran ...
system, support of people, support of quality management system.
These can be plotted in a "fishbone"
Ishikawa diagram to help identify potential sources of measurement variation.
Goals
The goals of a MSA are:
# Quantification of measurement uncertainty, including the accuracy, precision including
repeatability
Repeatability or test–retest reliability is the closeness of the agreement between the results of successive measurements of the same measure, when carried out under the same conditions of measurement. In other words, the measurements are taken ...
and
reproducibility
Reproducibility, also known as replicability and repeatability, is a major principle underpinning the scientific method. For the findings of a study to be reproducible means that results obtained by an experiment or an observational study or in a ...
, the stability and linearity of these quantities over time and across the intended range of use of the measurement process.
# Development of improvement plans, when needed.
# Decision about whether a measurement process is adequate for a specific engineering/manufacturing application.
ASTM Procedures
The
ASTM
ASTM International, formerly known as American Society for Testing and Materials, is an international standards organization that develops and publishes voluntary consensus technical standards for a wide range of materials, products, systems, an ...
has several procedures for evaluating measurement systems and test methods, including:
* ASTM E2782 - Standard Guide for Measurement Systems Analysis
* ASTM D4356 - Standard Practice for Establishing Consistent Test Method Tolerances
* ASTM E691 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
* ASTM E1169 - Standard Guide for Conducting Ruggedness Tests
* ASTM E1488 - Standard Guide for Statistical Procedures to Use in Developing and Applying Test Methods
ASME Procedures
The
American Society of Mechanical Engineers
The American Society of Mechanical Engineers (ASME) is an American professional association that, in its own words, "promotes the art, science, and practice of multidisciplinary engineering and allied sciences around the globe" via "continuing ...
(ASME) has several procedures and reports targeted at task-specific
uncertainty budgeting and methods for utilizing those uncertainty estimates when evaluating the
measurand
Measurement is the quantification of attributes of an object or event, which can be used to compare with other objects or events.
In other words, measurement is a process of determining how large or small a physical quantity is as compared ...
for compliance to specification.
They are:
* B89.7.3.1 - 2001 Guidelines for Decision Rules: Considering Measurement Uncertainty Determining Conformance to Specifications
* B89.7.3.2 - 2007 Guidelines for the Evaluation of Dimensional Measurement Uncertainty (Technical Report)
* B89.7.3.3 - 2002 Guidelines for Assessing the Reliability of Dimensional Measurement Uncertainty Statements
AIAG Procedures
The
Automotive Industry Action Group (AIAG),
a non-profit association of automotive companies,
has documented a recommended measurement systems analysis procedure in their MSA manual.
This book is part of a series of inter-related manuals the AIAG controls and publishes,
including:
* The measurement systems analysis manual
* The
failure mode and effects analysis (FMEA) and Control Plan manual
* The
statistical process control (SPC) manual
* The
production part approval process (PPAP) manual
Note that the AIAG's website has a list of "errata sheets" for its publications.
See also
*
Measurement uncertainty
In metrology, measurement uncertainty is the expression of the statistical dispersion of the values attributed to a measured quantity. All measurements are subject to uncertainty and a measurement result is complete only when it is accompanied by ...
*
Round robin test
*
Verification and validation
References
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Measurement