euramet.pr-k3.a.1 - final report · 2017. 5. 9. · 1 euramet.pr-k3.a.1 final report luminous...

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EURAMET.PR-K3.a.1

Final report

Luminous intensity bilateral comparison

using lamps as transfer standards

between

LNE (France) and INM-RO (Roumania)

Gaël Obein Mihai Simionescu

Jimmy Dubard Amadeu Seucan

Jean Bastie.

4 January 2012

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Preamble The EURAMET project 823, “Comparison of luminous intensity and luminous flux using lamps as transfer standards” between LNE (formerly BNM), France and INM-RO, Romania was intended to link the INM-RO realized candela and the lumen to the CCPR key comparison reference values and to demonstrate the INM-RO calibration measurement capability in calibrating tungsten standard lamps for transferring these units. A technical protocol for these two comparisons was agreed upon by the participants and submitted to the EURAMET and to the CCPR for approval. The two comparisons were registered on BIPM key comparison data base with the numbers EURAMET.PR-K3.a.1 for luminous intensity and EURAMET.PR-K4.1 for luminous flux, respectively. Abstract The EURAMET project 823, “Comparison of luminous intensity and luminous flux using lamps as transfer standards” between LNE (formerly BNM), France, and INM-RO, Romania, has linked the INM-RO realized candela to the CCPR key comparison reference values. The comparison was registered on BIPM key com-parison data base with the numbers EURAMET.PR-K3.a.1. The comparison has been piloted by LNE. It has been carried out by successive calibrations of a group of four travelling standard lamps in the two laboratories. The lamps were first calibrated by INM-RO, then calibrated by LNE and calibrated by INM-RO in order to check for any drift or instability. The measure-ments have been performed over the period November 2004 to June 2006. According to the results of the comparison, the Degree of Equivalence of the candela realized by INM-RO to the Key Comparison Reference Value of CCPR-K3 is – 0,72 % with an expended uncertainty (k = 2) of 2.14 %.

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Bilateral comparison of luminous intensity between LNE, France and INM, Romania

(KCDB reference No: EURAMET.PR-K3.a.1)

Final Report

Gaël Obein, Mihai Simionescu, Jimmy Dubard, Amadeu Seucan, Jean Bastie.

Contents

1 Introduction ............................................................................................................................................ 42 Organization ........................................................................................................................................... 4

2.1 Participants ..................................................................................................................................... 42.2 Form of comparison ....................................................................................................................... 42.3 Duration ......................................................................................................................................... 4

3 Description of the artefacts .................................................................................................................... 53.1 Characteristics of the lamps ........................................................................................................... 53.2 Transport and handling .................................................................................................................. 5

4 Measurement conditions ........................................................................................................................ 54.1 Laboratories environment .............................................................................................................. 54.2 Lamp operation details ................................................................................................................... 54.3 Measurand ...................................................................................................................................... 54.4 Alignment ...................................................................................................................................... 6

Alignment procedure at LNE ................................................................................................................. 6Alignment procedure at INM-RO .......................................................................................................... 6

5 Analysis of measurements results .......................................................................................................... 65.1 INM-RO results summary .............................................................................................................. 65.2 LNE results summary .................................................................................................................... 75.3 Comparison of results .................................................................................................................... 7

Comments on the uncertainties .............................................................................................................. 8Comments on the lamps behaviour ........................................................................................................ 9

6 Measurement uncertainties .................................................................................................................... 96.1 LNE measurement uncertainty ...................................................................................................... 96.2 INM-RO measurement uncertainty .............................................................................................. 10

7 Measurement traceability and procedures ........................................................................................... 147.1 Measurement traceability and procedures at LNE ....................................................................... 147.2 Measurement traceability chain and procedures at INM-RO ...................................................... 14

8 Link to the CCPR KCRV ..................................................................................................................... 159 Conclusion ........................................................................................................................................... 1610 References ........................................................................................................................................ 16A Appendix A.1 Analysis of uncertainties A.2 Detailed measurement results A.2.1 Measurements at INM-RO (ROUND I)

A.2.2 Measurement at LNE-INM A.2.3 Measurements at INM-RO (ROUND II)

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Introduction The Laboratoire National de Métrologie et d’Essais, LNE (France) and the Institutul National de Métrologie, INM-RO (Romania) agreed in September 2004 to conduct a bilateral comparison on luminous intensity using a group of incandescent lamps as transfer standards. The aims of the comparison were: ¨ To link the INM-RO realized unit candela to the CCPR K3.a reference value [1]. ¨ To demonstrate the INM-RO measurement capability in calibrating tungsten luminous intensity stand-

ard lamps. A technical protocol following the guidelines established by the BIPM and taking into account the technical protocol of the key comparison of luminous intensity organized by the CIPM was agreed upon. The comparison and its protocol were approved by the CCPR and registered within the KCDB with the comparison number: EURAMET.PR-K3.a.1. 1 Organization The comparison was organized and conducted within the EURAMET Project 823.

1.1 Participants

Address Person in charge Contact Laboratoire National de Metro-logie d`Essais LNE-CNAM 61 Rue du Landy 93210 La Plaine Saint Denis France

Jean Bastie, Gaël Obein Tel : +33 1 58 80.87.88 Fax : +33 1 58 80 89 00 e-mail: [email protected].

National Institute of Metrology – Romania Sos. Vitan Barzesti Nr 11 42 210 Bucharest Romania

Mihai Simionescu, Amadeu Seucan

Tel: (+4021) 334 50 60 Fax: (+4021) 334 53 45 e-mail:[email protected]

The LNE, France, acted as the pilot laboratory.

1.2 Form of comparison The comparison was carried out by successive calibrations of a group of travelling standard lamps in the two laboratories. Details on the transfer standards are given in section 3 of this report. The lamps were first calibrated by INM-RO. Then they were hand carried to LNE, where a second calibra-tion was performed. After being carried back to INM-RO, the lamps were calibrated again in order to check for any drift or instability.

1.3 Duration The measurements were performed over the period November 2004 to June 2006.

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2 Description of the artefacts 2.1 Characteristics of the lamps

The lamps were of tungsten incandescent, OSRAM Wi 40 G and Wi 41 G type, provided by INM-RO. The serial numbers were 91/8 and 91/12 for Wi 40 G, and 711 and 823 for Wi 41 G. All the lamps were operated in vertical position with the cap down and at a color temperature cT = (2800 ± 30) K. The electrical parameters are given in Table 1. The fifth column shows the percentage presentation of the difference between the voltages 21,UU measured in June 2006 and November 2004, respectively, divided by their average.

Table 1 – Electrical parameters of the standard lamps used for the comparison

Lamp serial number

dc current

(A)

dc voltage 1U Nov. 2004

(V)

dc voltage 2U June. 2006

(V) 12

122UUUU

+-

711 5,5689 28.77 28.80 0.093 % 823 5,6288 29.18 29.20 0.057 % 91/8 5,6120 29.87 29.92 0.178 %

91/12 5,6120 30.10 30.11 0.033 % Mean 0.090 %

The mean increase of the voltages of all lamps is 0.09 % and thus, the relative increase of the luminous intensity values is expected to be twice that much.

2.2 Transport and handling The lamps were hand carried from one laboratory to the other. After each transportation the lamps were thoroughly inspected and the electrical parameters were checked. There was no reported damage of the transfer standard lamps during the transportations. 3 Measurement conditions

3.1 Laboratories environment

Both laboratories performed the measurements at an ambient temperature of (23 ± 1)°C and a relative hu-midity of (50 ± 10)%.

3.2 Lamp operation details In order to avoid premature ageing, the lamps were operated at a color temperature of 2800 K. For all lamps, the positive voltage was applied to the central connector.

3.3 Measurand The measurand was the luminous intensity of the lamps, measured in a direction normal to the filament plane and intercepting it in the centre of it’s rectangular area. The direction to the photometer is through the mask for Wi 41G lamps and for Wi 40 G lamps to that side marked on the bulb with “Meßseite”.

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3.4 Alignment Alignment procedure at LNE The measurements were carried out on a photometric bench the length of which was 4 meters. The lamp-holder was set on a mechanical holder with 6 degrees of freedom. Two viewfinders were used for position-ing the lamp on the photometric bench. One was mounted on the optical axis of the bench and was used to adjust the centre of the lamp filament on the bench axis and a vertical projection of the lamp axis. The second viewfinder was mounted horizontally and perpendicular to the optical axis of the photometric bench and was used to adjust the plane of the filament perpendicularly to the axis of the bench. This viewfinder and was also used as the origin for the distance measurement. The distance for a luminous intensity meas-urement was about 3 meters and was not changed for all the lamps (reference and transfer standards). Alignment procedure at INM-RO The lamp mount allowed for fine positioning and angular adjustment of the installed lamp so that the lamp axis was vertical and the direction of the optical axis of the bench was normal to the filament plane and intercepted it in it’s geometrical centre. An optical device allowing image projection of the lamp filament on a grounded glass with a cross hair was used for this purpose. The cross hair was placed in the origin of the optical bench. The measuring distance was of 2,800 m. Several baffles were used for stray-light reduction. 4 Analysis of measurements results

4.1 INM-RO results summary

The measurement at INM-RO were carried-out from 28 October 2004 to 08 November 2004 for the first round and from 25 May to 10 June 2006 for the second round by using a set of 3 standard photometers realising the candela (a more detailed calculation is given in the appendix).

Table 2 – Results of the measurements at INM-RO

Lamp serial number Luminous intensity (cd)

Rel. Std. Dev. (%)

Rel. Std. uncertainty (%)

91/8 Round 1 253.09 0.14 0.90 Round 2 254.49 0.25 0.90

mean 253.79 0.29 0.90 91/12 Round 1 255.01 0.05 0.90

Round 2 254.90 0.27 0.90 mean 254.96 0.27 0.90

711 Round 1 228.31 0.17 0.90 Round 2 228.95 0.26 0.90

mean 228.63 0.31 0.90 823 Round 1 239.77 0.19 0.90

Round 2 239.86 0.31 0.90 mean 239.82 0.36 0.90

averaged rel.std.dev. 0.31 0.84

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The value of the INM-RO measurements assigned to one lamp is the mean of the measurements of two rounds. The relative standard deviation of this mean value listed in the lines denoted with “mean” and de-termined as the square root of the sum of squares. The average of these means is denoted as “averaged rel. std. dev.” with the number 0.31% and is stated in the last line of table 2. This relative standard deviation is uncorrelated and mainly originated in the alignment of the standard lamps. It is a significant contribution to the estimated constant relative uncertainty of 0.90% for the relative standard uncertainty in the last column. The square root of the difference of the squares of these two numbers ( )%31.090.084.0 22 -= is the part in the combined uncertainty common to each uncertainty creating correlation.

4.2 LNE results summary

The measurements at LNE were carried-out from 21 December 2005 to 3 January 2006 by comparison with a set of 3 standard lamps maintaining the luminous intensity unit and having taken part in the CCPR-K3.a key comparison. For a more detailed calculation see the appendix. The results are summarised in table 3. As before, from the estimated uncertainty of 0.51% the constant part 0.46%, which creates correlation, is separated.

Table 3 Results of the measurements at LNE

Lamp serial number Luminous intensity Rel. Std. Dev. Rel. Std. uncertainty (cd) (%) (%)

91/8 257.57 0.22 0.51 91/12 257.84 0.30 0.51 711 233.50 0.12 0.51 823 244.58 0.20 0.51

averaged rel.std.dev. 0.21 0.46

4.3 Comparison of results

The results of the two laboratories were compared by calculating the relative difference of the luminous intensity values assigned by each participant to a lamp using the following formula:

( ) ( )( ) ( ) ( )[ ] ( ) ( )[ ]R

2relR,

2rel

2rel

2rel

2rel

Rrelrel

R

R,RR,R,

R,

0;01

;11

cuIucuIuu

cucucc

IcIc

II

III

iii

i

i

i

i

i

iii

+++=D

¹¹==

-××

=-=-

=D (1)

where iD is the relative difference for the thi lamp

iI is the luminous intensity value of the thi lamp assigned by INM-RO urel(Ii) is the relative standard deviation on Ii

iIR, is the luminous intensity value of the thi lamp assigned by LNE urel(IR,i) is the relative standard deviation on IR,i

c factor with associated uncertainty ( ) %84.0rel =cu common to all values of INM-RO (Table 2) Rc factor with associated uncertainty ( ) %46.0Rrel =cu common to all values of LNE (Table 3)

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The difference ( )( ) ( )( )åå==

DDD=Dn

ii

n

iii uu

1

2

1

2 1 for the comparison can be determined as mean value either

with the (absolute) uncertainties of equ. (1) taken as weights or as arithmetic mean. The common part is the significant contribution and thus, the arithmetic mean is sufficient.

( ) ( ) ( ){ }úúû

ù

êêë

é

÷÷ø

öççè

æ+÷

÷ø

öççè

æ+=D

D=D

åå

å

==

=

n

i i

in

i i

i

n

ii

IIu

IIcucu

nu

n

1 R,

2

2

1 R,R

2rel

2rel2

2rel

1

1

;1

(2)

In this comparison the ratios 1R, @ii II of the luminous intensity values are nearly unity and the uncertain-ties ( ) ( ) ( ) ( )RR,, IuIuIuIu ii ¢@¢@ associated by one laboratory to the values of the lamps in the batch are very similar and taken as constant for all lamps with luminous intensities R, II ¢¢ . With these assumptions finally the averaged difference and the associated uncertainty can be calculated.

( ) ( ) ( ) ( ) ( )[ ]R2rel

2relR

2rel

2rel

2rel

1 R,

1

;11

IuIun

cucuu

II

n

n

i i

i

¢+¢++=D

-=D å= (3)

With these two equations and the values of the tables 2 and 3 the final results of the comparison between the calibration of the standard lamps carried-out at INM-RO and LNE are given in table 4.

Table 4 – Results of the comparison between INM-RO values and LNE values.

Lamp serial INM-RO LNE Relative difference (cd) (cd)

91/8 253.79 257.57 -0.01469

91/12 254.96 257.84 -0.01119

711 228.63 233.50 -0.02086

823 239.82 244.58 -0.01950

Mean difference D = -0.01656

common rel. uncert. 0.0084 0.0046 averaged rel. std dev. 0.0031 0.0021

Std. uncertainty associated to mean difference ( )Drelu = 0.00976

Comments on the uncertainties The result in table 4 shows a difference %7.1-=D between the calibrations carried out in the INM-RO and the LNE. From the associated relative uncertainty ( ) %98.0rel =Du an expanded relative uncertainty

( ) %96.1rel =DU for (k = 2) can be calculated. Then the agreement (A) is calculated from the formula:

( ) ( )R, cucu( ) ( )Rrelrel , IuIu ¢¢

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( )DD

=relU

A (4)

A value 85.0=A is found, which shows a good agreement with both laboratories. Comments on the lamps behaviour The results obtained for the lamps of the OSRAM Wi 41 G type, serial numbers 711 and 823 are very homogenous (discrepancy 0.18 %) while the results for the lamps OSRAM Wi 40 G serial numbers 91/8 and 91/12 are less homogenous (discrepancy 0.39 %). Moreover the difference between the two types of lamps is quite large (discrepancy 0.73 %. This difference in the behaviour may be due to the fact that the Wi 41 G type lamps have a black shade which limits the luminous flux to that emitted by the filament itself. The Wi 40 G type lamps are not provided with such a shade. Consequently the flux reflected by the lamps bulb is also taken into account and according to the practical baffling one may obtain a larger dispersion of the values. 5 Measurement uncertainties The measurement uncertainties were estimated according to the ISO Guide to the Expression of Uncertainty in Measurement. The incandescent lamps were operated at dc-current in a fixed distance and care was taken to reduce any straylight and correct for all known errors. The ambient conditions are standard and do not affect the results. Then the luminous intensity is calculated from:

( )

( ) ( ) ÷÷ø

öççè

æD-D×-D---++=

×=

.......2

21

;

agingrelstray1

02

PL

v

12

0

JmIyydd

dTFcorr

corrsydTI

e (5)

Were ( )TI0 is the luminous intensity when the lamps is operated perfectly. T is the color temperature of the emitted radiation. d is the distance between the lamp filament and the photometer limiting aperture. 1y is the photocurrent corrected for straylight and offset 0y . vs is the luminous responsivity (determined for CIE illuminant A) corr is a correction factor with about unity value. ( )TF is the spectral mismatch correction as function of colour temperature. Ld is the displacement of the lamp. Pd is the displacement of the photometer. e is the misalignment of the lamp. strayD is the relative correction for straylight mI =7.0 is the coefficient for corrections of relative lamp current differences relJD is the relative difference in the lamp current setting. agingD is the relative effect of aging

5.1 LNE measurement uncertainty At LNE, the lamps were calibrated by substitution method as comparison with 3 standard lamps maintaining the luminous intensity unit and having participated to the CCPR-K3.a comparison. These were lamps type Wi 41 G from OSRAM running at a colour temperature of (2800 ± 15) K, the same colour temperature as the INM-RO lamps.

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The photometer head from LMT, used for the comparison was very well V(l) corrected. No correction and no uncertainty were applied for the spectral matching factor of the photometer head for this comparison. The other contributions to the combined uncertainty are summarised in the table 5. The substitution method with reference lamp standards (index “R ”) reduces the combined uncertainty. Provided the noise of the power supply is negligible and the photometer is well matched to ( )lV , then most of the corrections in equ. (5) cancel out of the model of evaluation, because the lamps are all of the same or nearly the same type and they have very similar characteristics. Equ. (5) divided by this equation written for the reference lamp reads:

( ) ( )

( ) ( ) ( ) ÷øö

çèæ D-D-D----+=

×=

...2121

;

R.agingstrayR,stray2R

2LR,L

R1

1R0R0

eeddd

cor

coryyTITI

(6)

The luminous intensity of the reference and two photocurrents are main part of the substitution method. The uncertainty of a correct alignment of the lamps and that of the straylight (mainly for the Wi40G-lamps) will contribute to the combined uncertainty.

Table 5 – Uncertainty budget of LNE for luminous intensity lamp comparison at LNE.

5.2 INM-RO measurement uncertainty

At INM-RO, the lamps were calibrated against three reference photometers. All measurements were per-formed within the reference temperature and humidity conditions so that no correction factors for ambient conditions were considered. Luminous responsivity of the reference photometers In order to determine the luminous responsivity of the reference photometers their absolute spectral respon-sivity ( )lisp, was characterised with the trap detector CL 01 as reference. The absolute spectral responsivity

Source Symbol 100 × Rel. Expanded uncertainty

Probability distribution. Divisor 100 × Rel.

Standard uncertainty No degrees of freedom

Luminous intensity of the reference iI ,0R 0.9 Normal 2 0.45 ∞

Photo-current measurement for reference

iy ,1 0.12 Normal 2 0.06 ∞

Photo-current measurement for test

iy ,1 0.12 Normal 2 0.06 ∞

Aging of the standard lamps Δaging 0.17 Rectangular √3

0.1

Distance (×2) α β γ x y z

iLd ,

0.05 0.17 0.05

0.009 0.009 0.02

Rectangular Rectangular Rectangular Rectangular Rectangular Rectangular

√3 √3 √3 √3 √3 √3

0.03 0.05 0.03

0.005 0.005 0.05

∞ ∞ ∞ ∞ ∞ ∞

Standard deviation 0.21 Normal 1 0.21 3

Combined uncertainty 0I Normal 0.52 ∞ Expanded uncertainty 1.04 Normal

(k=2) ∞

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( )ltraps of the trap detector is traceable to the LNE spectral responsivity primary reference, a cryogenic ra-diometer.

A substitution method ( ) ( ) ( )( ) ( )lll

ll ii

i Cii

ss p,trap

p,trapp, ××= was used for the evaluation of the photometer spec-

tral responsivity values. The photocurrents ( )liip, and ( )ltrapi were measured and a correction factor ( )liCp, was applied to take into account measurement errors from out-of-band-straylight, non-linearity, inhomoge-neity in the reference plane etc. The absolute spectral responsivity ( ) ( )ll iii sss r,,mp, ×= is divided in two factors: an absolute responsivity is ,m at the wavelength of peak responsivity and a function ( )lisr, of relative responsivity normalised to unity at that wavelength. The actual area 2

prAi ×p= of the measuring aperture was estimated by direct measurement of its diameter pr on an Abbe comparator in six directions [2] and a final averaging. The photometer luminous responsivity is expressed as:

( ) ii

iii C

TFKsA

s ,linAm

,m,v ×

××

= (7)

where index “ i ” refers to the thi reference photometer with 31 ££ i : is ,v is the luminous responsivity of the reference photometer determined from equ. (1);

iA is the area of the limiting aperture of the reference photometer (m2). It was measured with an

Abbe comparator. Repeated measurements of the diameter were performed on six different directions then the computed areas were averaged. The resulting area was of about 29 E-6 (m2) with minutes differences from one photometer to another. The associated standard uncertainty of the areas were estimated to be of 0.06 E-6 (m2) (0.20 %). is ,m is the absolute peak spectral responsivity of the photometer (A/W). It was spectrally meas-ured against the INM spectral responsivity reference (the CL 01 radiometer) traceable to the LNE-INM cryogenic reference radiometer. Depending of the considered photometer, values of about 0,250 (A/W) with an associated standard uncertainties of 0.0006 A/W (0.25 %) were found. lm/W683m =K is the maximum luminous efficacy of the CIE standard observer. iC ,lin is a correction factor for the photometer non-linearity having a value of 1.0000. Its associated uncertainty (estimated with the double aperture method in previous studies) was of 0.0002. ( )ATFi is the colour correction factor employed in equ. (7) computed according to equ. (8) from the spectral distribution of CIE illuminant A with colour temperature K2856A =T :

( )( )

( ) ( )òò

××

××=

lll

lll

dsS

dVSTF

ii

r,A

AA

)( (8)

Its value was computed to be ( ) 107.1A =TFi with an estimated standard uncertainty of 0.0044. where: )(A lS is relative spectral distribution of CIE illuminant A with colour temperature K2856A =T ;

( )lV is the relative luminous efficacy function of the CIE standard observer;

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( )lisr, is the function of relative spectral responsivity of a photometer. It was measured against the INM spectral responsivity reference (the CL 01 radiometer) traceable to the LNE-INM primary reference. The comparison was performed on the INM (monochromator) spectral comparator. A 1.5 nm spectral band-width and a step of 3 nm were used. Further parabolic interpolation was used to derive step 1 nm values used for computing the F value. Spectral responsivity measurements were characterised by standard uncer-tainties ranging from 0.20 (%) at peak wavelength to 2.0 (%) at the wings, where the available signal was quite low. Also, the values varied from one photometer to another but just one set of results is given in this report. The uncertainty budget of the luminous responsivity of a photometer is given in Table 6. Table 6 Uncertainty budget of the luminous responsivity of the standard photometers at INM-RO

evaluated from the model in equ. (1) ( ) ii

iii C

TFKsA

s ,linAm

,m,v ×

××

= .

Nr Quantity

Symbol Value Uncert.

)( ixu Sens.coeff

ic Type

Prob.distrib. D

OF )( ii xuc ×

10-9*A/lx iii sxuc ,v/)(×

% 1 Matching factor ( )ATFi 1.107

(one) 0.0044

(one) -8.643*10-9

A/lx B

normal ¥

-0.0380 -0.3975

2 Peak responsiv-ity is ,m 0.24909

(A/W) 0.0006 (A/W)

3.841*10-9 W/lx

B normal

¥

0,0230 0.00241

3 Reference pho-tometer area iA 29.041*10-6

(m2) 0.050*10-6

(m2) 0.3295*10-3 A/(lx*m2)

B normal

¥

0.016 0.167

4 Correction factor for non-linearity iC ,lin 1.0000

(one) 0.0002 (one)

9.568 *10-9 (A/lx)

B normal

¥

0.00191 0.020

Luminous res-ponsivity is ,v 9.568 *10-9

(A/lx) ¥

0,0472 (nA/lx)

0,432

Luminous intensity measurements The measurand luminous intensity is expressed as:

FIjii

ji CCisdI ×××= sup,,ph,v

2

,v, (9)

where : d is the lamp-photometer distance (m); is ,v is the luminous responsivity of the thi standard photometer (A/lx) of table 6;

jiphi ,, is the current (A) of the thi photometer measuring the thj lamp; supIC is a correction factor ( 0000.1sup @IC ) due to the uncertainty of the lamp DC-current. LampI . ( ) ( )Lamprelsuprel IumCu I ×= ; 5.6@m . The value was experimentally estimated for a dc current A5.5=I determined with an associated uncertainty ( ) A0026.0Lamp =Iu . Thus, the absolute uncertainty of the correction factor is ( ) ( ) 0031.05.5/0026.05.61LampLampsupsup =××=××= IIumCCu II .

( ) 0000,1A == mFF TTC is a correction factor for the lamp luminous intensity due to the

uncertainty associated to its distribution temperature. The exponent 064.0-»mF was es-timated with a standard uncertainty of 0.003. Thus, for distribution temperatures

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( )K302800±=T the uncertainty of the correction factor calculated ( ) ( ) 00067.02856/30064.01 =××=××= TTumFCCu FF

The luminous intensity uncertainty budget is given in Table 7. Table 7 – Uncertainty budget of the luminous intensity measurement at INM-RO

Evaluated from the model in equ. (3) FIjii

ji CCisdI ×××= sup,,ph,v

2

,v,

Nr Quantity Sym

bol Value

ix Uncer-tainty

)( ixu

Sensitivity

ic Type prob.

distribu-tion.

DOF )( ii xuc ×

.(cd)

Rel. std. unc.

( ) v/ Ixuc ii ×

(%) 1 Luminous responsivity

is ,v @9.568

@0,0472 26.041 B

5.3 @1.2292

5.4 @0.50%

(nA/lx) (nA/lx) (cd*lx/nA) normal 2 Photo-current measurement jii ,,ph

@2.095 @1.24E-10 1.20E+09 B

@0.1488 @0.060% nA (A) (cd/A) normal

3 Lamp-photometer distance d 2.8237 2.80E-03 178 B

5.4.1.1 0.4984

5.4.1.2 0.20%

(m) (cd/m) normal 4 Correction factor supply

supIC 1.0000 3.10E-03 250 B

0.775 0.31% (one) (cd) normal

5 Correction factor for mis-match FC 1.0000 0.0007 250 B

@0.1750 @0.070%

(one) (cd) normal A component @250.00 @1.5330 @0.61%

(cd) 6 Repeatability 0.450 1 normal 20 0.4500 0.18%

(cd) (one) luminous intensity

vI 253.61 normal 1.547 0.90

Discussion : Every value obtained with each of the three photometers is the mean of 20 values.

å=

=

==20j

1jvijvijvi I

201II with FsupIj,i,ph

i,v

2

vij CCIsdI ×××= (4)

The reported value is the mean of the values obtained with the three photometers.

¥

¥

¥

¥

¥

14

å=

===

3

131 i

iviviv III (5)

6 Measurement traceability and procedures

6.1 Measurement traceability and procedures at LNE The reference standard used by LNE was a group of three lamps of OSRAM Wi 41 G type, with serial numbers 927, 936 and 963. The reference lamps were supplied in such a way to have a colour temperature of (2800 ± 15) K. The three lamps are part of a larger batch of lamps maintaining the candela realised at LNE. These three lamps have been used in the CCPR K3.a comparison. The LNE measurements were performed by substitution of the reference lamps and the test lamps exactly at the same position on the photometric bench. The distance from the filament of the lamps to the photometer was approximately 3 meters. Several baffles carefully placed on the photometric bench were used for re-ducing stray light but for taking into account for the total flux coming from the bulb of the Wi 40 G lamps. The procedure used for the measurement was as it follows. A standard lamp from LNE was measured first, then the four lamps of INM-RO were measured and then the same standard lamp of LNE was measured again to check the stability of the measurement. The warm up time of the lamps was 15 minutes. The detail of the measurements results is given in appendix A-2.

6.2 Measurement traceability chain and procedures at INM-RO The measurement traceability of the INM-RO measurements is schematically shown in Fig. 1.

Fig. 1: INM-RO measurements traceability

15

Reference standard and method. The INM-RO candela realization is based on narrow band spectro-radiometric measurements and is main-tained on a group consisting of three filtered detectors using Hamamatsu S 1337 BQ photodiodes and pre-cision apertures with nominal diameters of 6 mm. The unit transfer to luminous intensity lamps is performed on a regular optical bench. Colour temperature and current supply. The lamps were operated at a colour temperature of 2800 K. The necessary dc current was adjusted by comparison with a colour temperature reference standard lamp calibrated by BIPM with an estimated stand-ard uncertainty of 15 K. The estimated standard uncertainty associated to the INM-RO measurement results was of 30 K while the estimated standard uncertainty in controlling the dc current trough the lamp filament was estimated to be of 0,04 %. 7 Link to the CCPR KCRV Basically, the calibration methods employed in this comparison are similar to that used by the LNE in the CCPR K3.a comparison (1997–1998). Hence it is possible to compare the results of the INM-RO measure-ments to the CCPR K3.a reference value. The results of the CCPR K3.a, as published in the Key Comparison Data Base show that the unilateral degree of equivalence of LNE is 0,89 % and has an associated expanded relative uncertainty of 0.60 %. Assuming that the LNE lamps have maintained their value since 1997-1998 comparison, it is possible to express the unilateral DoE of the INM-RO. According to the guidelines for bilateral comparison, the unilateral degree of equivalence of INM-RO is given by:

𝐷INM-RO = 𝐷LNE +𝑦INM-RO 𝑦LNE − 1fromaverageofartefacts

where 𝐷INM-ROis the unilateral DoE for INM-RO 𝐷LNE = 0,89%is the unilateral DoE for LNE, calculated during the KCPR K3.a. 𝑦INM-RO 𝑦LNE − 1 = ∆ = −1,7% is the average value of the ratio between the INM-RO average result and the LNE average result for the 4 lamps that have circulated in this bilat-eral comparison, subtracting unity to obtain a DoE (see table 4 p7).

DINM-RO = 0,98%-1,70% = -0,72%

The uncertainty on the unilateral degree of equivalence of INM-RO is given by

𝑢² 𝐷INM-RO = 𝑢INM-ROD + 𝑢D 𝑥refCCPRK3.a

+ 𝑢LNE,CCPRK3.aD

linkingquality

+ 𝑢LNE,BCD

BilateralComparison

Where

𝑢INM-RO is the declared total relative uncertainty of the INM-RO for luminous intensity cal-ibration (𝑢INM-RO =0,90%, see p14 of this report)

16

𝑢 𝑥ref is the relative standard uncertainty associated with the Key Comparison Reference Value (𝑢 𝑥ref = 0,09%, see KCDB on BIPM website). 𝑢LNE,CCPRK3.a is the declared total standard uncertainty of LNE during the CCPR K3.a com-parison (𝑢LNE,CCPRK3.a= 0,52%, see CCPR K3.a final report) 𝑢LNE,BC is the relative standard uncertainty associated with uncorrelated effects (random uncertainty) of the LNE during the bilateral comparison (𝑢LNE,BC= 0,21%, see p7 of this report).

𝑢 𝐷INM-RO = 0,90² + 0,09² + 0,52² + 0,21² = 1,07%

The uncertainty component of the unilateral DoE is given as an expanded uncertainty

𝑈 𝐷INM-RO = 2𝑢 𝐷INM-RO = 2,14% 8 Conclusion In the framework of the EURAMET Project 823, LNE-France and INM-RO have carried out a comparison of luminous intensity using standard lamps. The aim of this comparison was to link the INM-RO realized candela to the CCPR K3.a reference value and to demonstrate the INM-RO capability in calibrating tungsten standards lamps. According to the results of the comparison, the Degree of Equivalence of the candela realized by INM-RO to the Key Comparison Reference Value of CCPR-K3.a is – 0,72 % with an expended uncertainty (k = 2) of 2.14 %. 9 References 1. G. Sauter, D.Lindner and M.Lindemann, “CCPR Key Comparison K3a of Luminous Intensity and

K4 of Luminous Flux with Lamps as Transfer Standards”, PTB Bericht Opt-62, Braunschweig, Ger-many, December 1999

2. M.Simionescu, Intermediate report on the EURAMET Project 741, www.EURAMET.org, 2004 3. M.Simionescu, A.Seucan, J.Bastie, B.Rougie, Candela realization at NIM-Romania; Uncertainty es-

timation, Proceedings of CIE Experts Workshop, Braunschweig, 2006 4. M. Simionescu, A. Seucan and J.Bastie, INM-Romania newly developed standards, Proceedings of

NEWRAD 2005

17

A Appendices A.1 Analysis of uncertainties In order to provide the necessary comparability, the uncertainties should be estimated and expressed ac-cording to ISO-GUM. The main components of the measurement uncertainties are:

A type: Repeatability of measurements values: the standard deviation of the results obtained in a set of measurements on the artefact, without realignment;

B type Uncertainty of the reference standard and uncertainty due to the positioning of the artefact under calibration; Uncertainty due to the measurement methods (lamps dc supply, photocurrents values, etc.);

Other relevant components: other relevant components specific to one or the other participant meas-urement technique.

18

A2 Detailed measurements results A2.1 Measurements at INM-RO (Round I) Reference number of lamp:91/8

Photometer Luminous Filament Lamp Transfer Number of rel. std. Cumulative number intensity current voltage rel. std. dev readings uncertainty burn time

(cd) (A) (V) % (%) (h)

FA 03-1a 253.48 5.6120 29.86 0.065 20 0.60 0.75 FA 03-2a 252.99 5.6120 29.87 0.065 20 0.60 1.5 FA 03-3a 252.81 5.6120 29.87 0.020 20 0.60 2.25

Mean 253.09 5.6120 29.867

rel. std. Dev. 0.14% 0.019% Reference number of lamp: 91/12 Photometer Luminous Filament Lamp Transfer Number of rel. std. Cumulative

number intensity current voltage rel. std. dev readings uncertainty burn time (cd) (A) (V) % (%) (h)

FA 03-1a 254.99 5.6120 30.09 0.070 20 0.60 0.75

FA 03-2a 255.16 5.6120 30.10 0.045 20 0.60 1.5 FA 03-3a 254.89 5.6120 30.10 0.085 20 0.60 2.25

Mean 255.013 5.6120 30.097

rel. std. Dev. 0.054% 0.019% Reference number of lamp: 711

Photometer Luminous Filament Lamp Transfer Number of rel. std. Cumulative


FA 03-1a 228.43 5.5689 28.77 0.080 20 0.60 0.75 FA 03-2a 228.47 5.5689 28.76 0.135 20 0.60 1.5 FA 03-3a 228.04 5.5689 28.78 0.080 20 0.60 2.25

Mean 228.313 5.5689 28.770

rel. std. Dev. 0.10% 0.035% Reference number of lamp: 823 Photometer Luminous Filament Lamp Transfer Number of rel.std. Cumulative


FA 03-1a 240.22 5.6288 29.18 0.050 20 0.60 0.75 FA 03-2a 239.79 5.6288 29.19 0.025 20 0.60 1.5 FA 03-3a 239.31 5.6288 29.18 0.030 20 0.60 2.25

Mean 239.773 5.6288 29.183

rel. std. Dev. 0.19% 0.020%

19

A2.2 Measurements at LNE-INM Table of luminous intensity of the test lamps (cd)

Series 1 2 3

Standard lamp à 927 (cd)

936 (cd)

963 (cd)

Mean value (cd)

Rel. std. de-viation Test lamp â

823 244.31 244.30 245.14 244.58 1.971E-03 711 233.40 233.29 233.81 233.50 1.174E-03

91/12 258.02 257.01 258.50 257.84 2.950E-03 91/8 257.71 256.95 258.06 257.57 2.203E-03

Table of voltage of the test lamps (V)

Lamp 823 711 91/12 91/8

Series 1 29.22 28.81 30.32 30.27

Series 2 29.23 28.81 30.37 30.18 Series 3 29.22 28.81 30.17 30.28

Mean value 29.223 28.810 30.287 30.243

Rel. std. deviation 1.976E-04 0.0E+00 3.437E-03 1.821E-03

Table of the final results for test lamps

Lamp 823 711 91/12 91/8

Current (A) 5.6288 5.5689 5.6120 5.6120 Voltage (V), value 29.223 28.810 30.287 30.243

Rel. Std. Dev. 1.976E-04 0.000E+00 3.437E-03 1.821E-03 Lum. intensity (cd) 244.58 233.50 233.50 257.84

Rel. std. Dev. 1.971E-03 1.174E-03 2.950E-03 2.203E-03

20

A2.3 Measurements at INM-RO (Round II) Reference number of lamp:91/8


(cd) (A) (V) % (%) (h)

FA 03-1a 253.76 5.6120 29.90 0.050 20 0.60 0.75 FA 03-2a 254.95 5.6120 29.93 0.135 20 0.60 1.50 FA 03-3a 254.75 5.6120 29.93 0.080 20 0.60 2.25

Mean 254.49 5.6120 29.920

rel. std. Dev. 0.25% 0.058% Reference number of lamp: 91/12



FA 03-1a 254.12 5.6120 30.10 0.023 20 0.60 0.75 FA 03-2a 255.26 5.6120 30.10 0.011 20 0.60 1.5 FA 03-3a 255.33 5.6120 30.12 0.015 20 0.60 2.25

Mean 254.903 5.6120 30.107




FA 03-1a 228.27 5.5689 28.80 0.012 20 0.60 0.75 FA 03-2a 229.25 5.5689 28.79 0.022 20 0.60 1.5 FA 03-3a 229.32 5.5689 28.80 0.018 20 0.60 2.25

Mean 228.947 5.5689 28.797



(cd) (A) (V) % (%) (h)

FA 03-1a 239.04 5.6288 29.21 0.012 20 0.60 0.75 FA 03-2a 240.06 5.6288 29.20 0.007 20 0.60 1.5 FA 03-3a 240.47 5.6288 29.19 0.012 20 0.60 2.25

Mean 239.857 5.6288 29.200

rel. std. Dev. 0.31% 0.034%

21

A2.4 Graphical presentations The Fig. A1 shows the relative drift of the lamps voltages over the burning time (At the LNE a burning time of 0.2 h for one series was assumed).

Fig. A1 The relative change of the lamps voltages as function of the burning time during the comparison. The slopes are between (1 to 7.5)*10-4 per hour. The values found by the LNE are also shown and are found significantly above the INM-RO values.

The Fig. A2 shows the relative drift of the luminous intensities over the burning time (At the LNE a burning time of 0.2 h for one series was assumed).

Fig. A2 The relative change of the lamps luminous intensities as function of the burning time during the comparison. The slopes are between (1 to 17)*10-4 per hour. The values found by the LNE are also shown and found to be significantly above the INM values.

y = 0.00075x - 0.00079y = 0.00021x - 0.00012y = 0.00034x - 0.00050y = 0.00012x - 0.00003

-0.00200

0.00000

0.00200

0.00400

0.00600

0.00800

0.01000

0.01200

0.01400

0.01600

0 1 2 3 4 5

INM 91/8INM 91/12INM 711INM 823LNE 91/8LNE 91/12LNE 711LNE 823Linear (INM 91/8)Linear (INM 91/12)Linear (INM 711)Linear (INM 823)

y = 0.00169x - 0.00246y = 0.00010x - 0.00034y = 0.00097x - 0.00124y = 0.00022x - 0.00215

-0.01000

-0.00500

0.00000

0.00500

0.01000

0.01500

0.02000

0.02500

0 1 2 3 4 5

INM 91/8INM 91/12INM 711INM 823LNE 91/8LNE 91/12LNE 711LNE 823Linear (INM 91/8)Linear (INM 91/12)Linear (INM 711)Linear (INM 823)

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