ASME B89.7.3.3 pdf free download

ASME B89.7.3.3-2003 pdf free download.GUIDEL INES FOR ASSESSING THE RELIABILITY OF DIMENSIONAL MEASUREMENT UNCERTAINTY STATEMENTS.
In an ideal situation, customers and suppliers will address the issue of measurement uncertainty when they discuss the product specificaions. Agreeing on the measurement pian, the corresponding magnitude of the measurement uncerainty, and the decision rule (if applicabie), wili avoid future disagreemenis regarding the acceptance/rejection of a pruduct. However, it is recognized that LWU experts can produce Lwu differenl uncerlainty statennenls often varying as much as 25% due to differing assumptious and dala (as described in sectiou 5). Resolving thesc differences al the contract siage is potentially less contentious than doing so after an argument develops over the acceptance or rcicction of the productl. 3.2 Disagreements Involving Single Measurement Systems In many situations there is only a singie measurement system; e.g.. a customer agrces to accepl the supplier s measurement results provided that the supplier uses suringent accepuance with a 100% guard band (i.e., the guard band equais the expanded uncerlainty). in his cxampic，a disagreemenl may arise if the cuslumer feels the supplier has underestimaied the measuremeni uncertainty. Although there is a single measuremenl system, the supplicr and the customer have developed differing uncertainty slatements. 3.3 Disagreements Involving Multiple Measurement Systems In some situations, a customer and supplier both make measurements, each having their own measure- ment system and uncertainty statement. There are two cases 10 consider: first, when a product characteristic is being measured to assign it a value, e.g.. the length of a gauge biock. and second. when a product character- istic is being measured to determine whether it conforms with spccifcations. In the first case, a best estimate of the value of the product characteristic is being sought. Two measure- menls, fron different teasuremenl syslems, will give a better estimale when their results are appropriately combined than will cach system independently，provided the uncertainty slatements associated with the measure- ment systenus auc valid. It is unlikely that the measure- ments performed by the supplier and the customer will yieid exaciy the same vaiue; however, agreement between the measurements is obtained by soime extent of overlap uf the uncertainty intervals. Tihe exlent of overlap should be specified in order to clearly identify when the partics are in disagreement. (This avoids disagreements on what constitutes a measurement dis- agreement) Therc arc several possiblc cascs of mctro- logical significance as shown in Fig. 1. Lct Xg and x be the mcasurement results of the supplier and customer, with respective cxpanded uncertainties of Us and Uc (both using a coverage factor of k = 2). Let△= xs一xd be the absolute value of the difference between the measurements. Figure I illustrates this case with five different pairs of measurements. The measurements are considered 10 be in disagreement when > Us + Uc and in agreement when is less than the minimum of either Us or U。In laboratory round robins, measurements are generally considered tu agrce wien A is less than or equal to the rool sum of squarcs (RSS) of the lwu expanded uncerlainties and in disagreement if is grcater than this quantity. Sometimes two different measurement systems arc uscd to dctermine if a product is in conformancc with spccifications and he outcomcs of the two mcasurc- ments differ, i.c., the acceptance or rcjection of the product is in dispute. This case can be separated into issucs involving the decision rule and issues involving the reliability of the uncerlainty statement. When two different parties each perform measurements on the same product, potential disagreements can arise due to inherent conflict in the decision rules. For example, if both the supplier and customer apply stringent accept- ance then the party with the larger guard band will typically reject more of the product. This concerns the decision rule sclection, not the uncertainty statements,and consequently is outside the scope of these guidelines.ASME B89.7.3.3 pdf download.