Conformity of the quality in the measures

Ins umen a ion Viewpoin 8 4 m1 The usual no a ion o unce ainly is shown in equa ion 1. Y = X ± U Equa ion 1. Typical no a ion o he unce ainly in a esul T aceabili y Acco ding o he de ini ion o CEM [1].” A aceabili y chain, see Fig.2., is a unb o- ken chain o compa isons, had es ablished all unce ain ies. This ensu es ha a measu emen esul o alue o pa e n is associa ed wi h e e ences o highe le els, up o p ima y s anda d.” CONFORmITY OF THE QUALITY IN THE mEASURES (1) Labo a o io de me ologia y Calib ación. Uni e sidad Poli écnica de Ca alunya. Vilano a i la Gel ú (2) Depa amen o de Elec ónica. Escola Poli écnica Supe io d’Enginye ia de Vilano a i la Gel ú. Abs ac - We’ll wan o implan he awa eness o he impo ance a measu emen ’s quali y ha mus ha e wi h sys ems acquisi ion o own design. The choice o sys em acquisi ion will be e y impo an because his sys em will mus ul ill ou expec a- ions. Keywo ds- acquisi ion’s sys em, aceabili y, unce ainly, accu acy I. INTRODUCTION In any me hod o acquisi ion’s sys em we mus hink he nex ques ion: “ he da a ha we’ll wan o acqui e ha e he su icien accu acy ha we wish?”. No - mally his concep is e y clea o he designe howe e we mus ha e answe ano he ques ion: “ he unce ainly o my sys em o measu e will be su icien ly small in o de ha om he da a acquisi ion could ex ac conclusions?”. II. BASIC CONCEPTS Unce ainly acco ding o he de ini ion o CEM [1] “The unce ainly is a quan i a- i e measu e o he quali y measu emen esul , which allows ha he measu e- men esul s should be compa ed wi h o he esul s, wi h e e ences, speci ica- ions o s anda ds”. The unce ainly is calcula ed by p obabili y Some he p obabili y dis ibu ion mo e used a e he no mal dis ibu ion and he uni o m dis ibu ion. A Fig. 1. We can see g aphically heses p obabili y dis- ibu ions calcula ed wi h a his og am: Albe Ga cia1,Da id Palme o1,E a Vaqué1,An oni mánuel2 p essu e a ia ions and I´ll need e alua e a ia ions a ound o 1 a m, and he esolu ion o he equipmen used is 0,5 a m, i can hink ha sys em is good o make he wo k. Such an analysis is no alid, because we mus calcula e he unce ainly sys em. In ac is possible ha he unce ain y’s sys em can be o e 1 a m and my acquisi ion sys em isn´ good o he wo k. Equa ion 2, acco ding o UNE-EN 30012 [2] we can ela e he expanded unce - ainly (U) o he equipmen wi h he alue o Tole ance (T) o he measu emen we wan o do. In ou case he ole ance is he minimum alue ha we wan o see, in he p e ious example is 1 a m. The alues 3 and 10 ha e he nex explica ion: The alue 3 indica e ha he sys em has he op alue o unce ainly compa ed o ole ance. In his case ou sys em has he minimum equi emen s o ha e an alue accep able. The alue 10 indica e ha ou sys em has a lowes alue o unce ainly com- pa ed o ole ance. This is an ideal case, bu i we wan o ge 10 usually he equipmen s ha we need a e e y expensi e. Fo his is eason, all equipmen s o sys ems mus pass a calib a ion by he manu ac u e , which will gi e he accu acy, by ou sel es h ough some in e nal me hod. The mos impo an is main enance he aceabili y chain. IV. TOLERANCE´S MODIFICATION One ime ha we calcula ed he unce ainly o ou measu e’s sys em, we mus know ha he minimum alue ha we wan o see no longe co esponds o he ini ial alue, because has been al e ed by unce ainly. Now ou ole ance (T) will ha e been modi ied and will become (T’). This a ia ion is showed in he Fig. 3.: III. SYSTEM ANALYSIS Be o e beginning he design o he sys em we mus e alua e he unce ainly ha mus ha e he sys em. Fo example i we choose a sys em o acqui ing o Fig.3. Tole ance’s modi ica ion o he p ocess V. SYSTEMATIC To de e mine he bes equipmen o he pu pose ha we wish, we mus choose ha equipmen o measu emen sys em. In he nex diag am, Fig. 4.,we can see he s eps o ollow o a good choice: Fig. 4. Diag ama de sis emá ica del p oceso VI. CONCLUSIONS We ca ied ou a sys ema ic s udy o make a choice acco ding o ou needs. In his way we can educe he pu chase p ice o equipmen and gi e a alida ion o he alue ha we wan o analyze. REFERENCES [1] Edición del Cen o Español de Me ología (CEM). “ la me ología ab e iada”. M-20557-2005. [2] No ma UNE-EN 30012.” equisi os de asegu amien o de la calidad de los equipos de medida. Pa e 1: Sis ema de con i mación me ológica de los equipos de medida (ISO 10012-1:1992). (Ve sión o icial EN 30012-1:1993)” Fig. 1. His og ams ep esen ing he no mal dis ibu ion and he uni o m dis- ibu ion espec i ely Equa ion 2. Rela ion be ween Tole ance (T) and expanded Unce ainly (U) Fig.2. La cadena de azabilidad