A Bi-Lateral Comparison of a 0.5 gram to gram Weight Set

Transcription

1 PL Report CMAM 6 A Bi-Lterl Comprison of.5 grm to.1 grm Weight Set M Rymond Centre for Mechnicl nd Acosticl Mecrology tionl Physicl Lbortory T eddington Middlesex nited Kingdom TWIILW Dr L ielsen Dnish Institte of Fndmentl Metrology Bilding 37 Anker Engelnds Vej 1 DK -28 Lyngby Denmrk ABSTRACT A bi-lterl comprison of.5 grm to.1 grm set of weights hs been crried ot between the tionl Physicl Lbortory (PL) nd the Dnish Institte of Fndmentl Metrology (DFM). The mss vles of sixteen ot of seventeen mesred weights gree to within the combined stndrd ncertinty (k=l) of the two lbortories. This represents n excellent greement nd gives confidence in the mesrements performed by both lbortories.

2 PL Report CMAM Crown copyright 1997 Reprodced by permission of the controller of HMSO ISS tionl Physicl Lbortory Teddington, Middlesex, nited Kingdom, TW11 OLW o extrcts from this report my be reprodced withot the prior written consent of the Mnging Director, tionl Physicl Lbortory; if consent is given the sorce mst be cknowledged nd my not be sed ot of context. Approved on behlf of the Mnging Director, PL, by Dr G Torr, Hed of Centre, Centre for Mechnicl nd Acosticl Metrology

3 1 ITRODCTIO 1 2 EQIPMET SED FOR COMPARISO STADARDS AD TRACEABILITY PL DFM BALACES PL DFM 2.3 AIR DESffY MEASREMETS PL Mesrements b 2.3.1c 2.3.1d Air Pressre Tempertre 3 3 Hmidity dew point 3 Crbon dioxide concentrtion DFM Mesrements Air Pressre b Tempertre c Hmidity dew point d Crbon dioxide concentrtion 4 3 WEIGI-llG SCHEME PL MEASREMETS DFM MEASREMETS 4 4 CERTAITIES PL Air Density Mss Stndrds Density of the weights Weighing Scheme Blnce DFM Vle of reference mss 6

4 4.2.2 Air Density Volmes of weights Centres of grvity of weights Blnce repetbility Scle fctor 7 5 RESLTS 7 6 COCLSIOS 8 7 SMMARY 8 8 REFERECES 9 Tble 1 Atmospheric Conditions Dring the Mesrements 1 Tble 2 Reslts of the Mss Mesrement t PL nd DFM 11 Tble 3 Comprison of reslts Obtined t PL nd DFM 12 Tble 4 PL ncertinty Bdget for PLW65 13 Tble 5 DFM ncertinty Bdget for LW65 14 Tble 6 Mss vles obtined for the dded fl weights in prt 'C' of PL W65 together with the vles obtined in April 1996 when the set PLW54 ws lst clibrted 15 Figre 1 Trcebility of PI Grms nd PLW43 16 Figre 2 Grph showing the chnge in mesred mss for PLW65 in April 1996 nd Jne 1996 reltive to the vles mesred in Jnry

5 PL Report CMAM 6 1 ITRODCTIO A bi-lterl comprison of.5 grm to.1 grm set of weights ws crried ot between the tionl Physicl Lbortory (PL), nited Kingdom nd the Dnish Institte of Fndmentl Metrology (DFM), Denmrk. This is the first comprison mde t this level by either lbortory nd both were keen to ensre tht greement between their mesrements ws within their estimted ncertinties for the weights. It ws greed tht PL wold provide set of weights for the comprison. The set of weights sed for this comprison ws spplied by Precis Blnces Limited. This set is identified s PLW65 prts 'C' nd 'D' nd is hosed in wooden box which contins two plstic lined comprtments, lbelled 'C' nd 'D'. Prt 'C' of the set comprises of nonmgnetic stinless steel polygonl wire weights of nominl mss.5 grm to.1 grm shped ccording to the OIML recommendtion [1]. Prt 'D' of the set is similr to prt 'C' except the shpe of ech weight is slightly ltered to distingish them from the prt 'C' weights. All of the weights hve n ssmed density of 8 5 kg m-3 bsed on the mesred density of lrger weights from the sme mnfctrer. The set ws prchsed from Precis in 1994 nd hs been weighed t PL in Febrry 1994 nd Mrch The weights hve not been sed for ny other prpose. The weights were clibrted t PL dring the period 24 to 29 Jnry They were then tken by ir to the EROMET Mss Contct Persons meeting in Mdrid on 5 Febrry 1996 nd hnded to the DFM representtive. The weights remined in Mdrid for five dys before being tken to Denmrk nd were clibrted by DFM dring the period 16 to 3 April The weights were retrned to PL on 2 My 1996 nd clibrted gin dring the period 13 to 21 Jne A frther clibrtion of prt 'C' of the set withot prt 'D' ws crried ot t PL dring the period 9 to 22 Agst EQIPMET SED FOR COMPARISO 2.1 STADARDS AD TRACEABILrrY PL Three stndrds of nominl mss 1 grm were sed to clibrte set PLW65. Two of the 1 grm stndrds re cylindricl stinless steel weights of stinless steel with volme of.1276 cm3 nd stndrd ncertinty of ::!:. 5 cm3. These weights re tken from 5 grms to 1 grm set known s PLW43, which hs n ssmed density of 784 kg m-3 bsed on the mesrement of the density of lrger weights from the sme mnfctrer. The third 1 grm stndrd is cylindricl weight of pltinm-iridim with volme of.469 cm3 nd stndrd ncertinty of.5 cm3. This weight is tken from 5 grms to 1 milligrm set known s PI Grms, which hs n ssmed density of kg m-3 bsed on mesrements mde by the Bord of Trde [2]. The three stndrds re trceble by sb-division to the Interntionl Prototype Kilogrm held t the Interntionl Bre of Weights nd Mesres (BIPM), throgh the K tionl Prototype Kilogrm o 18 (Kg 18) which ws lst clibrted by BIPM in Figre 1 shows the trcebility of PI Grms nd PLW 43 bck to Kg 18. 1

6 2.1.2 DFM The Ig weight WIg in the weight set DFM 431 ws sed s reference stndrd for the clibrtion. This weight is mde of stinless steel nd hs volme of.1259 cm3 mesred with stndrd ncertinty of :t. 25 cm3 by hydrosttic weighing. The mss of WIg hs been mesred by sbdivision from the lkg weight Wlkg in the weight set DFM 432. The weight Wlkg hs been clibrted directly ginst the Dnish tionl Prototype Kilogrm K48, which is trceble to the Interntionl Prototype Kilogrm throgh periodic clibrtions t BIPM; K48 ws lst clibrted t BIPM in Jne BALACES PL Two blnces were sed for this comprison. A Srtoris 54 single-pn blnce ws sed to clibrte the weights before they were sent to DFM. This blnce hd cpcity of 4 grms with redbility of.1 g nd stndrd devition of.2 g on the repetbility of twenty consective redings, the blnce being rrested between ech reding. When the weights were retrned from DFM they were clibrted sing Mettler ME22 single-pn blnce. This blnce hs cpcity of 3 grms with redbility of.1 g nd stndrd devition of.3 g on the repetbility of twenty consective redings. The Agst 1996 clibrtion of prt 'C' of the set ws crried ot sing the Srtoris 54 blnce, which in Jne 1996 hd been modified by Srtoris to hve cpcity of 5 grms. The blnce is now known s the Srtoris CSS. It hs the sme redbility of.1 g nd following re-ssessment shows stndrd devition of.3 g on the repetbility of twenty consective redings DFM The clibrtion of the msses were performed on Mettler M3 single pn mss comprtor. This comprtor hs cpcity of 3 g nd resoltion of.1 g. The stndrd devition of the mss difference of two weights A nd B mesred sing the ABBA weighing scheme is typiclly.5 g. 2.3 AIR DESITY MEASREMETS When weights of different volme were being compred correction ws mde for the ir boyncy which necessitted knowing the ir density t the time of the weighing. The ir density ws clclted from the for prmeters, ir pressre, tempertre, hmidity dew point nd crbon dioxide concentrtion, sing the empiricl eqtion recommended by CIPM [3]. Sections nd describe the eqipment sed for the mesrement of ech prmeter nd the ssocited stndrd ncertinty. Tble 1 gives the rnges of the mesred tmospheric conditions for ech clibrtion mde t FL nd DFM. 2

7 2.3.1 PL Mesrements Air Pressre The ir pressre ws mesred sing Drck DPI 14 vibrting cell brometer whose ncertinty, incorporting n element for drift between clibrtions, is :t.5 mbr t coverge fctor of k=l. This corresponds to stndrd ncertinty of:t.6 kg m-3 in ir density b Tempertre The tempertre ws mesred sing n Edle thermistor which hs clibrtion ncertinty of :t.3 C t coverge fctor of k=l. When combined with the ncertinty of the tempertre grdient cross the blnce nd the drift of the instrment between clibrtions, the ncertinty becomes :t.2 C which corresponds to stndrd ncertinty of:t.9 kg m-3 in the ir density c Hmidity dew point The hmidity dew point ws mesred sing Michell series 3 cooled mirror hygrometer. This hs n ncertinty of:t.11 C t coverge fctor of k=l. This combined with the ncertinty de to the dew point grdient cross the lbortory nd n element for the drift between clibrtions gives totl ncertinty of :t.25 C which corresponds to stndrd ncertinty of:t.7 kg m-3 in the ir density d Crbon dioxide concentrtion This hs not been mesred dring this comprison bt ws ssmed to be 4 ppm with n ncertinty of :t 5 ppm. This gives stndrd ncertinty in the ir density of :t. 3 kg m DFM Mesrements Air Pressre The ir pressre ws mesred sing Digiqrtz Digitl Brometer, model 74-16B from Proscientific Inc. The stndrd ncertinty of the pressre mesred with this instrment hs been estimted to :t 5 P, corresponding to stndrd ncertinty of :t.5 kg m-3 in the clclted ir density b Tempertre The tempertre ws mesred with PtlOO resistnce thermometer; its resistnce is mesred with Kelvimt Trnsmitter 432 mde by Brster. The resistnce thermometer nd the trnsmitter re clibrted s seprte nits. The mesred resistnce is converted to 3

8 PL Report CMAM 6 tempertre sing second order clibrtion crve fitted to the clibrtion dt obtined for the PtlOO element. The stndrd ncertinty of the mesred tempertre hs been estimted to :t. 6 mk, corresponding to stndrd ncertinty of :t.. 3 kg m-3 in the clclted ir density c Hmidity dew point The hmidity dew point of the mbient ir ws mesred sing Michell series 4 cooled mirror hygrometer. The stndrd ncertinty of the mesred dew point hs been estimted to :t.1 K corresponding to stndrd ncertinty of:t.4 kg m-3 in the clclted ir density d Crbon dioxide concentrtion The crbon dioxide content of the mbient ir ws mesred sing Briiel & Kjr photocosticl Mlti Gs-monitor, type 132. The stndrd ncertinty of the mesred crbon dioxide content hs been estimted to :t 2 ppm corresponding to stndrd ncertinty of :t.1 kg m-3 in the clclted ir density. 3 WEIGHIG SCHEME 3.1 FL MEASREMETS The set ws clibrted by FL employing sb-division method [4] nd weighing in doble sbstittion mode. Corrections for ir boyncy were mde sing the CIPM forml. o corrections were mde for the difference in the height of centre of grvity s this is negligible. The mss vles of the weights were clclted from the mss differences obtined dring the clibrtion sing lest sqres method [5]. Prt 'C' of the set ws clibrted withot prt 'D' in Agst To llow sb-division, dditionl weights of known mss were clibrted s prt of the set. These weights re listed in Tble 6 long with the mss vles obtined for these weights in this clibrtion nd known vles from when the ll the weights in the set were clibrted in Jly DFM MEASREMETS The clibrtion ws by sbdividing the mss of the reference stndrd WIg ccording to DFM's internl method [6]. Two sbdivisions were crried ot independently. One on prt C nd one on prt D of the set. In order to crete two sets sitble for sbdivision, the weights listed in Tble 7 were dded to both sets. The mss differences between selected weight combintions A nd B were mesred by weighing ccording to Bord's sbstittion principle. One difference ws bsed on for redings tken in the seqence ABBA, nd this seqence ws repeted 5 times. Ech mss difference observed ws corrected for ir boyncy nd differences in the verticl position of the centres of grvity of the weights. The ir boyncy corrections were clclted from the 4

9 volmes or densities known priori nd ir densities clclted from continos mesrements of pressre, tempertre, hmidity nd CO2 content sing the CIPM forml. From the observed, corrected mss differences the nknown msses hve been clclted for ech decde by the method of lest sqres sing the mss of WIg s restrint. The mss corrections obtined for the dditionl weights sed in ech of the two sbdivisions re given in Tble 7 together with the verge of their known vles obtined since CERTAITIES 4.1 PL The combined stndrd ncertinty in the mss of ech weight hs been clclted by estimting n ncertinty for ech of the identified contribting fctors nd combining these contribtions in qdrtre, in ccordnce with the 'ISO gide to the expression of ncertinty in mesrement' [7], to give combined stndrd ncertinty t coverge fctor of k=l Air Density The combined stndrd ncertinty in the ir density mesrement is mde p of the stndrd ncertinty de to ech of the mesred prmeters, s well s the stndrd ncertinty from the empiricl eqtion. The stndrd ncertinty ssocited with the eqtion is estimted to be :t. 12 kg m-3[8], which when dded in qdrtre to the ncertinties in the mesred prmeters, gives combined stndrd ncertinty of :t. 9 kg m-3 in the ir density mesrement t k=1 coverge fctor. The combined stndrd ncertinty contribtion rising from the ir density mesrement is lwys less thn :t.1i.lg Mss Stndrds The stndrds sed in the clibrtion of the set ech hve stndrd ncertinty of :t. 5 mg ssigned to them t the time of their clibrtion. These re ll derived from the stndrd ncertinty of:t.2 7 mg ssigned to the K tionl Prototype Kilogrm o 18. This stndrd ncertinty incldes n element for the ncertinty in the mss gin model [9]. A component to llow for the drift in the vles of the mss stndrds is inclded in their stndrd ncertinties Density of the weights The estimted stndrd ncertinty rising from the ssmed density of the stndrds nd the weights being clibrtion is :t 1 kg m-3. This leds to n ssocited stndrd ncertinty of :t. 2 mg in the mss vles ssigned to the weights. 5

10 PL Report CMAM 6 Weighing Scheme The weighing scheme sed llows for redndncy of dt. The stndrd ncertinty for ech weight in the weighing scheme is clclted by lest sqres nlysis [5] Blnce The PL convention is to tke the stndrd ncertinty of the blnce to be eql to the stndrd devition of twenty consective redings tht hve been crried ot dring its ssessment. However, it my be considered tht the blnce stndrd ncertinty is eql to the estimted stndrd ncertinty of twenty consective redings (ie the stndrd devition divided by -.In-l), which gives more optimistic ncertinty vle. 4.2 DFM The stndrd ncertinties of the mesred msses hve been estimted s described in ref. [6], which is consistent with the principles lid down in the Gide [7]. The following sorces of ncertinty were considered. Vle of reference mss Bsed on the clibrtion history the mss of WIg ws set to 1 g mg with stndrd ncertinty of:!::. 7 mg. Air Density As described in previos section, the stndrd ncertinty of the ir density hs been estimted to ::t.11 kg m-3. The reltive stndrd ncertinty of the recommended forml itself hs been estimted to ::t 6.5 E-5, corresponding to stndrd ncertinty of ::t.8 kg m-3 in the clclted ir density, which is inclded in the bove estimte. Volmes of weights The volmes ssigned to the DFM weights hve been bsed on either hydrosttic weighing of the prticlr weight, or clclted from ssmed densities for the weight mterils. The volmes of the PL W65 weights nd the ssocited stndrd ncertinties hve been clclted from density vle 85 kg m -3 nd stndrd ncertinty ::t 1 kg m-3 specified by PL Centres of grvity of weights The verticl position of the grvity centres of the PL W65 weights were ssmed to be rectnglrly distribted within:!::.5 Inm. 6

11 4.2.5 Blnce repetbility For ech decde the stndrd devition of single mss difference mesrement (sing the ABBA weighing seqence) ws clclted from the residls of the lest sqres fit performed. This stndrd devition ws propgted to stndrd ncertinty for ech weight in the decde Scle fctor Before the clibrtion ws crried ot, the scle fctor of the mss comprtor were mesred to be mg/div with stndrd ncertinty of:t.2 mg/div. 5 RESLTS The dt relting to the tmospheric conditions dring the mesrements re given in Tble 1. The dtes nd reslts of ll the clibrtions mde t PL nd DFM re given in Tble 2. The differences between the mss vles obtined by PL nd those obtined by DFM re given in Tble 3. The dt indicte time-dependent loss in mss for ll the weights. The grph in Figre 2 shows the differences of the reslts obtined by DFM in April 1996 nd PL in Jne 1996 from the reslts obtined by PL in Jnry It lso illstrtes the trend with which the weights re drifting. This trend is lso spported by the reslts of the two previos clibrtions mde by PL in Febrry 1994 nd Mrch The reslts obtined by PL in Jne 1996 gree more closely with the DFM reslts thn the Jnry 1996 reslts. This is my be de to the fct tht the weights hd trvelled, fter the first set of mesrements were mde, by n indirect rote inclding five dy sty in hotel where the tmospheric conditions re not idel. The effect of drift in the mss vles of the weights my be considerbly redced by tking n verge vle from the two PL clibrtions nd compring these vles with the reslts obtined by DFM. Colmn for of Tble 3 shows the differences clclted in this mnner. The mss vle ssigned to the 1 mg weight in prt 'c' of the set s reslt of the initil clibrtion t PL in Jnry 1996 clibrtion is significntly different to the vles ssigned in the other clibrtions. The weight sffered slight dmge de to mishndling dring this clibrtion. When it ws clibrted by DFM the mss of the weight ws comprble to the vles obtined by PL in Febrry 1994 nd Mrch The mss vles obtined by PL in Jne 1996 nd Agst 1996 gree exctly with the DFM clibrtion. The weight ppers to hve temporrily gined mss fter it ws dmged!. Throghot sbseqent clcltions the mesrements on this weight hve been ignored. This behvior is similr to tht exhibited by 1 kg weight tht ws dmged t PL in 1994 [9]. The reson for this behvior is not nderstood. 7

12 6 COCLSIOS Idelly more stble set of weights wold hve been sed in comprison sch s this. When the drift in the mss vles of the weights is tken into ccont there is good greement between the two lbortories. The mss differences of sixteen ot of the seventeen weights nder considertion (94 %) gree to within the combined stndrd ncertinties (dded in qdrtre) of the two lbortories. A coverge fctor of k=l, indictes level of confidence of pproximtely 67 %. Therefore, reslt in which 94 % of the mesred vles gree to within the combined stndrd ncertinties my be considered stisfctory. The stndrd ncertinties of the mss vles reported by DFM re smller thn those qoted by PL for ll nominl vles except.5 grm. The PL ncertinty bdget, shown in Tble 4, my be considered to be pessimistic s it incldes n element for the repetbility of the blnce which is bsed on the stndrd devition of nmber of repeted mesrements rther thn the on the estimted stndrd ncertinty of this ssessment. If the PL ncertinty bdget is mended to inclde the estimted stndrd ncertinty of the blnce performnce, s shown in the finl colmn of Tble 4, the combined stndrd ncertinties re redced. An ssessment of the reslts of the comprison bsed on these redced ncertinties revels tht thirteen ot of seventeen weights (76 %) gree to within the combined stndrd ncertinty of the two lbortories. This my lso be considered stisfctory reslt. The DFM ncertinty bdget is shown in Tble 5. 7 SMMARY A comprison of the clibrtion reslts chieved by PL nd DFM (the two prticipting lbortories) for set of stinless steel weights of.5 grm to.1 grm hs been mde. The reslts indicte tht the mss of the weights sed ppers to be chnging with time in predictble mnner. When the mesrement reslts re interpreted llowing for this timedependent drift, the greement is stisfctory when compred to the combined stndrd ncertinties of mesrement of the two lbortories. 8

13 PL Report CMAM 6 8 REFERECES [1] Interntionl recommendtion 111. Weights of Clsses Ell E21 FII FII MIl I. OIML, [2] Lewis, S.L. nd Hvrd, D.C. History of kilogrm 18 nd Other Importnt K Reference Mss Stndrds. PL Report MOT 1, [3] Dvis, R.S. Metrologi, 29, pp 67-7, [4] Lewis, S.L. nd Dvidson, S. Clibrtion of Mss Stndrds by Sbdivision of the Kilogrm. PL Report MOM 96, 199. [5] Hnt, R.A. The Assignment of Vles to Set of weights. PL Report MOM 5, 1981 [6] DFM qlity system docment Q2KALS2: Clibrtion Methods -Mss ( ) [7] Interntionl Orgniztion for Stndrdiztion, Genev, Switzerlnd. Gide to the Expression of ncertinty in Mesrement. First Edition, [8] Gicomo, P. Metrologi, 18 pp 33-4, 1982 [9] Severn, I. nd Rymond,.M. The Assignment of Vles to PL's 1 kg Stndrds Following the Third Periodic Verifiction of Prototype Kilogrms. PL Report MOT 2,

14 Tble 1: Atmospheric Conditions Dring the Mesrements Air Pressre Temperhlre Dew Point Crbon Dioxide (mbr) (OC) (OC) (ppm) Air Density (kg m-3) PL Minimm Jn '96 Mximm ncertinty :t.5 :t.1 :t.25 :tso :t. 9 DFM Minimm 1] Apr '96 Mximm ncertinty :t.5 ::!:.6 ID.l :t 2 :t. 11 PL Minimm Jn '96 Mximm ncertinty :t.5 :t.1 :t.25 :t5 :!:. 9 PL Minimm Ag '96 Mximm ncertinty :!:.5 ::!:O.O1 :t.25 :t5 :t. 9 The ncertinties stted in this tble re qoted t the coverge fctor of k=l 1

15 o-j \ \ (X) I \ \ (X) \,..J \ '\ \ I \ '\ \,.,J \ \ I \ \ \ \C \ ] fj) cis o Z Os cis. rn \C \ I " " I: fj) " ",..J z fj) fj) -.s fj) ' E-- >.. '"' ::J rn rn!is 1- :::> (Ij \ \ \ <:=5 (f) '- \ It') t'.. '8 : Cfj \ In Oi I '-t4 T"4 '\ '\ t"-..-; Cf") ; ; \ (:::) \ ; ; ; ":t' t'-. \ \ ; ; ('f') \,Q \ \ n ; c ; E5.& :E 1-4 '".&...s ' II.-,4 PL Report CMAM 6 M I: t'-.. \ \ C! If:) c:: 'ot4...,.q4 I \ Ct).-t \ It') C1').-; C1").-; rt') Cf') Lr) Lr) 8 c:5 Ir) Ir) ") ; ; 8; ; C'") Inl C1 Inl g::1 \' ; Cf') '-! l!') C1 C;') f"\' c::5 l!) \ \ \ \ \ \ \ Cf') \C \ Ci') c: ") \ <X> OO! \ I, Lr) (::) ("Ii I q \ \ \ \ ; I.t) <::\ <::\ <::\ <::\ <::\ Cf) I,C It') \C ") \ (:) \ \ d IJ').-t - \D C'! \ \ \ \ \ rt) d to... Cf1 ; C"! \C \ \ \ \ \ \ \ T-4 \ \ \ \ \ c:: \ \ \ \ C'! If) \ \ \ (::) In i '1 CX) \ \ \ \ \ l. \ \ \ (:) C'! C'! '-t4 \ (:::) lf1 t'-. If) lc).." = t +1 bli =1- +1 bl\ ) >.. c =1- bc hi'\ +1 b() +1 CI) CI)!IS >'E I I-t?;!\S bd 11

16 Tble 3: Comprison of Reslts Obtined t PL nd DFM ominl Mss g O.5C Difference between PL&DFM (Jn) & (Apr) Difference between DFM & PL (Apr & Jn) /.lg g Difference between PL nd DFM (llowing for drift)! g.35 Combined Stndrd ncertinty OFM & PL O.5D O.2C O.2D DAD.5.1 C O.lD O.O5C O.O5D O.O2C O.O2D C O.OID C D C D C 1.6*.*.8*.5*.1 D The ncertinties stted in this tble re qoted t the coverge fctor of k=l g.6 * This weight ws dmged dring the Jnry 1996 clibrtion t PL. 12

17 r-:mam6 r) os:..j 2 ;j i:;- (\3 5..J c(\3 bo. ;3.. b ' I ;3 'E I ] cn >.. ] "O"O'E : "; ">.g "... "!IS O *:::> ofo.?:-'.rn :s: t: CJ) o :e-. 1- "< s= J.= s=.!j.o (Ij rj) J r ;3. lis lis -lis lis ) :E S ) c ) "tj ] o.. -!IS "8 E z >. "O"O'E cc ' -s " ):::> :e- ] "tj o 1 t ci5 CD co \ c:: (X) C").-i <=) C1 In :1 1 CI') ") \ C1 In C'i \r) \ 8 \ M \., '2 \ ; C"! 1 CX) ; \ n \ Cf) c: c:5 CI') \r) C") \ 8 (X) ; M l!) 1-4 ; I/) i 1 Cf) Cf) ; ; \ Cf') ") \ 13 C"! Cf) Cf) <=:.-; q t Ir) C'"? Lr) (::) C"! m m \ ; If) ; n 1 1 '8 Ir) If) L() C? ; I 'I, C1').-I \ c: ; ; ; C1") C1 '8 C1') <=! 8; II.Y. '.9 -E. ] g. :E " 2-.:g :c. "' "' ' "' "' 2!. :e-. -:s Po ' -.c -:S :e-. ' "' ' "' "' 2!. S ] :e-. ' >- "'O ' "' Po ' "'.6-6]8.

18 ] s= J..o cis, -cis m.. 8; C() ; IX) ; Ci') rt) ; \ C'1 ; \.-; ; <X) <X) c::: '\ ; \ ; c: '\ r") ; \ d \.-; ; ; ; ; \ /:'-.. ' bd s=... :8 ' rs= I-i <1J Ī co o,?;-,..., > co lis (1)1-4'-"' CO " > "bz> Ṇ -I If) ; (X) c;j '8 c: I \ g; rl ;.-I 25 C!.-I ; In 8: Ir) 8; C! \ ; ; \ Lt") ; \ \ c: t \D 1 \ CX),..; ; I:-.. M <=> ; <=> to... ; n I:'-.. Cf) ; '\ ; ; to-. CX) \ 8 d CX) CI') ; ; (:) I:'-.. C1 \ ; ; If) c::: r Lr) c: R cx:> 8; \ \ t ; r... \ <;:) <;:) <;:) <;:) <;:) <;:) (::) lrj II \D -.E - "E ] C.f\.c:- "tj co b CI) Q.I '--' '\ In Cf) \ ; 8 ; (X) RI CX) R ; n l() \ 8 :5 ; <::) \.C) C1 M C=? ; t... ; Cf') ; C (;() '8; ; '8 ; C'") C1 ; ; 1,. ] g. -.. Ct) - I Ir) :E I E-4 fo Of II') ( bi b( C b(.-! d bl d (:\ bl In, c b( I ( <=5 Ol ( '8 q b( bl bl.-; ; bl :: '"d Ct) Ct) E-- 14

19 PL Report CMAM 6 II) \C \ \ - :f;:.s " E..g II) :s Ī >.:S -:S.! bo! i I I I I.- II) :c bo. I 'i ( " " I "O 2!. I..8: ":'= :s - 1 > I Z -:.. I E-o.,f:: s= ',= :9- c c 1- lc) \..= I.. I II) I..- II) II) I :t;- :::> \ \ e < >, "E. (Ij \ \ \ co E +I E +1 e ;j < '?. E 5.- :c...j z - t'-..oo OOOO OOOOO O(x)\DCf) \ \ Cf) t... OOOO I + T + + I C1 Q oot OO.q. \ ('t) t.q. oooo I + I + + I d '-t4 '-t4 oooooooot'-..t'-..!:'.. t'-.. t'-.. "'" bobobobo boboqqqq QQ OOOO oooc-;o <::) <::) <::) <::) <::) <::) <::) <::) <::) c:5 c:5 n ; (:) t:f"\, IrI \ \.-. "' tis -.g -tis > tis 1- > tis.. 1-.t: t:. "' "' "' tis. -- "' tis -.g..t: 1-1- tis r:,: tis 15 ) fl \ :s:...:i ") \D,..J '? Q -(II E Q -[tl >. c= 1- 'E \ \ \ 1-4 Q.. :e- '? 's e +1 ::J :t::- lis t: CIJ co S co E \ \ \ b() ': e P.. < :r;..:g Q 1. bo +1 ::J 'r:-'" '; 's.:?f '. lis.... t: :s E +1 ) E e +1 '- Cf") OOOOO Or") r") 'ot' 'ot' I I I + I ;.-; ;.-; O\.-;OO O.-;OO I I I + I \ C") C r,.. r,.. OOO I I I + I + Cj") \.-; C Cf\ Cf\ ooooooo ooooooo oo"'*' t'-. +.j...j...-;.-;.-; ci O\O\O\.-. t'-.. \ \,Q + + c bd bd S S bd bd bd bd bt bdgggg S S S.-; C"! C"!.-;.-; " <X> \ \ \ <X> <X> <X> <X>.-; C") C") C") C") C") C") C") OOOQQOOO

20 Figre 1: Trcebility of PI Grms ndplw 43 Kg 18 Pi-If kilogrm PI Grms Pt-Ir 5 g -.1 g AI.5 g -.1 g Kg A & B Pt-Ir kilogrms PL W 36 Two stinless steel kilogrms PLW43 Stinless steel set SOOg-lg 16

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