ASME B89.7.3.3:2003 pdf download

ASME B89.7.3.3:2003 pdf download.GUIDELINES FOR ASSESSING THE RELIABILITYOF DIMENSIONAL MEASUREMENT UNCERTAINTY STATEMENTS
1 SCOPE
1.1 Objective This technical report provides guidance in assessing the reliability of a statement of measurement uncertainty in question, that is, in judging whether that stated uncertainty can be trusted to include the values that could reasonably be attributed to the measured quantity (measurand) with which that stated uncertainty is asso- ciated. 1.2 Applicability This report is most applicable to statements of uncer- tainty in the results of dimensional measurements based upon the IS0 Guide to Expression of Uncertainty in Measurement (GUM). (Also called ANSVNCSL 2540-2.) 1.3 Purpose This technical report helps parties to avoid potential, or resolve actual, disagreements over the magnitude of a stated measurement uncertainty, particularly when that uncertaínty is part of a determination of conformity of a manufactured product to a dimensional specifi- cation.
2 DEFINITIONSI
acceptance zone: the set of values of a characteristic, for a specified measurement process and decision rule, that results in product acceptance when a measurement result is within this zone.’ decision rule: a documented rule, meeting the require- ments of section 3 of ASME B89.7.3.1, that describes how measurement uncertainty will be allocated with regard to accepting or rejecting a product according to its specification and the result of a measurement. expanded uncertainty: quantity defining an interval about the result of a measurement that may be expected to encompass a large fraction of the distribution of values that could reasonably be attributed to the measur- and. See GUM, 2.3.5. guard band: the magnitude of the offset from the specification limit to the acceptance or rejection zone boundasr.measurand: particular quantity subject to measure- ment. See VIM 2.6.9 N:l decision rule: a situation where the width of the specification zone is at least N times larger than the uncertainty interval for the measurement result.” rejection zone: the set of values of a characteristic, for a specified measurement process and decision rule, that results in product rejection when a measurement result is within this zone.” specijìcation zone (of an instrument or workpiece): the set of values of a characteristic between, and including, the specification iimits.12’ 13, l4 stringent acceptance: the situation when the accept- ance zone is reduced from the specification zone by a guard band(s).l5. l6 stringent rejection: the situation when the rejection zone is increased beyond the specification zone by a guard band.17 uncertainty interval (of a measurement): the set of values of a characteristic about the result of a measure- ment that may be expected to encompass a large fraction of the distribution of values that could reasonably be attributed to the measurand.
3 THE NATURE OF DISAGREEMENTS IN UN CERTA1 NTY STATEMENTS
3.1 General in an ideal situation, customers and suppliers will address the issue of measurement uncertainty when they discuss the product specifications. Agreeing on the measurement plan, the corresponding magnitude of the measurement uncertainty, and the decision rule (if applicable), will avoid future disagreements regarding the acceptance/rejection of a product. However, it is recognized that two experts can produce two different uncertainty statements often varying as much as 25% due to differing assumptions and data (as described in section 5). Resolving these differences at the contract stage is potentially less contentious than doing so after an argument develops over the acceptance or rejection of the product. 3.2 Disagreements Involving Single Measurement Systems in many situations there is only a single measurement system; e.g., a customer agrees to accept the supplier’s measurement results provided that the supplier uses stringent acceptance with a 100% guard band (i.e., the guard band equals the expanded uncertainty). In this example, a disagreement may arise if the customer feels the supplier has underestimated the measurement uncertainty.