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है”ह”ह

IS 16106 (2012): Method of Electrical and PhotometricMeasurements of Solid State Lighting (LED) Products [ETD23: Electric Lamps and their Auxiliaries]

© BIS 2012

B U R E A U O F I N D I A N S T A N D A R D SMANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002

February 2012 Price Group 7

IS 16106 : 2012

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Indian Standard

METHOD OF ELECTRICAL AND PHOTOMETRICMEASUREMENTS OF SOLID STATE

LIGHTING (LED) PRODUCTS

ICS 29.140.99

Electric Lamps and Their Auxiliaries Sectional Committee, ETD 23

FOREWORD

This Indian Standard was adopted by the Bureau of Indian Standards, after the draft finalized by the ElectricLamps and Their Auxiliaries Sectional Committee had been approved by the Electrotechnical Division Council.

This standard has been developed for the electrical and photometric measurements of solid state lighting (SSL)products commonly known as LED. While many other standards for photometric measurements of light sourcesand luminaires are available, these standards are separated for measurement of lamps of luminaires with LED asthe light source. Since the current SSL products are in the forms of luminaires or lamps, and LED light sourcesin the luminaires are not easily separated as replaceable lamps these existing standards cannot be applied directlyto SSL products. This necessitates the use of absolute photometry. The Annex A in this standard provides thedescription of how absolute photometry varies from relative photometry, which have historically been the lightingindustry standards. Thus, this standard provides test methods addressing the requirements for measurement ofSSL products. Since SSL technologies are still at their early stages, requirements for measurement conditionsand appropriate measurement techniques may be subject to change at any time as the SSL technologies advance.

This standard is based on IES-LM-79-2008 ‘IES approved method for the electrical and photometric measurementsof solid state lighting products’, issued by the Illuminating Engineering Society of North America. Referencegiven to other standards have been changed to corresponding Indian Standards.

For the purpose of deciding whether a particular requirement of this standard is complied with, the final value,observed or calculated expressing the result of a test or analysis, shall be rounded off in accordance with IS 2 : 1960‘Rules for rounding off numerical values (revised)’. The number of significant places retained in the rounded offvalue should be the same as that of the specified value in this standard.

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IS 16106 : 2012

Indian Standard

METHOD OF ELECTRICAL AND PHOTOMETRICMEASUREMENTS OF SOLID STATE

LIGHTING (LED) PRODUCTS

1 SCOPE

This standard covers the procedures to be followed andprecautions to be observed in performing reproduciblemeasurements of total luminous flux, electrical power,luminous intensity distribution, and chromaticity, ofsolid state lighting (SSL) products commonly knownas LED products for illumination purpose, understandard test conditions.

The method covers LED based SSL products withcontrol electronics and heat sinks incorporated, thatis, those devices that require only ac mains power or adc voltage power supply to operate. This standard doesnot cover SSL products that require external operatingcircuits or external heat sinks (for example, LED chips,LED packages, and LED modules). This standardcovers SSL products in a form of luminaires (fixturesincorporating light sources) as well as integrated LEDlamps (see 3.7). This standard does not cover fixturesdesigned for SSL products sold without a light source.This standard describes test methods for individual SSLproducts, and does not cover the determination of theperformance rating of products, in which individualvariations among the products should be considered.

SSL products as defined in this standard utilize LEDs(including inorganic and organic LEDs) as the opticalradiation sources to generate light for illuminationpurpose. An LED is a p-n junction semiconductordevice that emits incoherent optical radiation whenbiased in the forward direction. White light is producedby LEDs using following two methods :

a) Visible spectra of two or more coloursproduced by LEDs are mixed, or

b) Emission (in the blue or ultraviolet region)from LEDs is used to excite one or morephosphors to produce broadband emission inthe visible region (Stokes emission).

For stand alone LED, constant current control is typical.This standard deals with integrated SSL productsincorporating the semiconductor device level currentcontrol, thus the electrical parameters of interest arethe SSL product’s input electrical parameters.

For special purposes, it may be useful to determinethe characteristics of SSL products when they are

operated at other than the standard conditions describedin this standard. Where this is done, such results aremeaningful only for the particular condition underwhich they were obtained and these conditions shallbe reported in test report.

The photometric information typically required for SSLproducts is total luminous flux (lumens), luminousefficacy (lm/W), luminous intensity (candelas) in oneor more directions, chromaticity coordinates, correlatedcolour temperature, and colour rendering index. Forthe purpose of this approved method, the determinationof these data shall be considered for photometricmeasurements.

The electrical characteristics measured for a.c.-powered SSL products are input r.m.s a.c. voltage, inputr.m.s a.c. current, input a.c. power, input voltagefrequency and power factor. For d.c.-powered SSLproducts, measured electrical characteristics are inputdc voltage, input d.c. current, and input power, For thepurpose of this standard, the determination of theseshall be considered for electrical measurements.

2 REFERENCE

The standard listed below contains provision which,through reference in this text, constitutes provision ofthis standard. At the time of publication, the editionindicated was valid. All standards are subject to revisionand parties to agreements based on this standard isencouraged to investigate the possibility of applyingthe most recent edition of the standard listed as follows:

IS No. Title

3646 (Part 1) : Code of practice for interior1992 illumination: Part 1 General

requirements and recommendationsfor working interiors

3 TERMINOLOGY

For the purpose of this standard, the followingdefinitions shall apply.

3.1 Electrical Measurement — Unit of measurementin volt, ampere and watt.

3.2 Photometric Measurement — Unit ofmeasurement in lumen and candela.

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IS 16106 : 2012

3.3 Chromaticity Coordinates — This is specified interm of the CIE recommended systems, the (x, y) or(u', v') chromaticity coordinates. To specify toleranceof chromaticity independent from correlated colourtemperature (CCT), the ( u', v') coordinates shall beused. The chromaticity can also be expressed by CCTand Duv (signed distance from the Planckian locus onthe CIE ( u', 2/3 u') diagram.

3.4 Regulation — Constancy of the voltage appliedto the SSL product under test.

3.5 Seasoning Time — Advance operation of the testSSL product for a given number of hours from thebrand new condition. Photometric data obtainedimmediately after this seasoning time is referred to asinitial data.

3.6 Stabilization — Operation of test SSL productsfor a sufficient period of time such that the electricaland the photometric values become stable. This is alsocalled warm-up time.

3.7 Integrated LED Lamp — An LED device withan integrated driver and a standardized base that isdesigned to connect to the branch circuit via astandardized lamp holder/socket (for examplereplacement of incandescent lamps with screw base).

LED luminaire refers to a complete LED lighting unitconsisting of a light source and driver together withparts to distribute light, to position and protect the lightsource, and to connect the light source to a branchcircuit. The light source itself may be an LED arrayand LED module, or an LED lamp.

3.8 Pre-burning — Operation of a light source priorto its mounting on a measuring instrument, to shortenthe required stabilization time on the instrument.

3.9 Photometer Head — A unit containing a detector,a V (Y)-correction filter, and any additional components(aperture, diffuser, amplifier, etc) within the unit.

4 GENERAL TEST CONDITIONS

4.1 General

Photometric values and electrical characteristics of SSLproducts are sensitive to changes in ambienttemperature or air movement due to thermalcharacteristics of LEDs.

4.2 Air Temperature

The ambient temperature in which measurements arebeing taken shall be maintained at 25°C ± 1°C,measured at a point not more than 1 m from the SSLproduct and at the same height as the SSL product.The temperature sensor shall be shielded from directoptical radiation from the SSL product and optical

radiation from any other source. If measurements areperformed at other than this recommendedtemperature, this is a non-standard condition and shallbe noted in the test report.

4.3 Thermal Conditions for Mounting SSL Products

The method of mounting can be the primary path forheat flow away from the devices and can affectmeasurement results significantly. The SSL productunder test shall be mounted to the measuring instrument(for example, integrating sphere) so that heatconduction through supporting objects causesnegligible cooling effects. For example, when a ceilingmounted product is measured by mounting at a spherewall, the product may be suspended in open air ratherthan directly mounted in close thermal contact withthe sphere wall. Alternatively, the product may be heldby support a material that has low heat requirementshall be evaluated for impact in measurement results.Also, care should be taken so that supporting objectsdo not disturb air flow around the product. If the SSLproduct under test is provided with a support structurethat is designated to be used as a component of theluminaire thermal management systems, the productshall be tested with the support structure attached. Anysuch support structure included in the measurementshall be reported.

4.4 Air Movement

The incidence of air movements on the surface of SSLproduct under test may substantially alter electrical andphotometric values. Air flow around the SSL productbeing tested should be such that normal convective airflow induced by device under test is not affected.

5 POWER SUPPLY CHARACTERISTICS

5.1 Wave Shape of a.c. Power Supply

The a.c. power supply, while operating the SSLproduct, shall have a sinusoidal voltage wave shape ata frequency of 50 Hz such that the r.m.s summation ofthe harmonic components does not exceed 3 percentof the fundamental during operation of the test item.

5.2 Voltage Regulation

The voltage of an a.c. power supply (r.m.s voltage) ofdc power supply (instantaneous voltage) applied to thedevice under test shall be regulated to within± 0.2 percent under load.

6 SEASONING (AGEING) OF SSL PRODUCT

For the purpose of new SSL products, SSL productsshall be tested with no seasoning or ageing.

NOTE — Some LED sources are known to increase theirlight output slightly during the first 1 000 h of operation; many

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IS 16106 : 2012

other LED sources do not follow such behaviour. The seasoningis not done because the increase of light output of LED productsbetween 0 h to 1 000 h, if occurs, is less than several percent,which does not result in significant changes in initial luminousflux or life of the products.

7 STABILIZATION OF SSL PRODUCT

Before measurements are taken, the SSL product undertest shall be operated long enough to reach stabilizationand temperature equilibrium. The time required forstabilization depends on the type of SSL products undertest. The stabilization time typically ranges from 30 minfor small integrated LED lamps to 2 h or more for largeSSL luminaries. The SSL ambient temperature asspecified in 4.2 and in the operating orientation asspecified in 6. It can be judged that stability is reachedwhen the variation (maximum to minimum) of at least3 readings of the light output and electrical power overa period of 30 min, taken at 5 min interval, is less than0.5 percent. The stabilization time used for each SSLproduct shall be reported.

For measurement of a number of products of the samemodel, stabilization methods other than those describedabove, for example, pre-burning of the product as givenin 3.8 may be used, if it has been demonstrated thatthe method produces the same stabilized condition tothat of the standard method described above.

NOTE — Same stabilized condition is achieved when themeasured total luminous flux is within 0.5 percent of thedeclared value.

8 OPERATING ORIENTATION

The SSL product under test shall be evaluated in theoperating orientation recommended by themanufacturer for an intended use of the SSL product.Stabilization and photometric measurements of SSLproducts shall be done in such operating orientation.

NOTE — The light emission process of an LED is not affectedby orientation. However, the orientation of an SSL productcan cause changes in thermal conditions for the LEDs used inthe product. And thus the light output may be affected byorientation of the SSL product. The orientation of the SSLproducts as mounted for measurement shall be reported withthe results.

9 ELECTRICAL SETTINGS

The SSL product under test shall be operated at therated voltage (a.c. or d.c.) according to the specificationof the SSL product for its normal use. Pulsed inputelectrical power and measurement synchronized withreduced duty cycle input power intended to reduce þ-njunction temperature below those reached withcontinuous input electrical power shall not be used forSSL product testing.

If the product has dimming capability, measurementsshall be performed at the maximum input power

condition. If the product has multiple modes ofoperation including variable CCT, measurement maybe made at different modes of operation and CCTs, ifnecessary, and such setting conditions shall be clearlyreported.

10 ELECTRICAL INSTRUMENTATION

10.1 Circuits

For d.c. input SSL product, a d.c. voltmeter and a d.c.ammeter are connected between the d.c. power supplyand the SSL product under test. The voltmeter shall beconnected across the electrical power inputs of the SSLproduct. The product of the measured voltage and thecurrent gives the input electrical power (wattage) ofthe d.c. powered SSL product.

For a.c. input SSL products, an ac wattmeter shall beconnected between the ac power supply and the SSLproduct under test, and a.c. power as well as inputvoltage and current shall be measured.

10.2 Uncertainties

The calibration uncertainties (see Note) of theinstruments for a.c. voltage and current shall be ≤ 0.2percent. The calibration uncertainty of the a.c.wattmeter meter shall be ≤ 0.5 percent and that for d.c.voltage and current shall be ≤ 0.1 percent.

NOTE — Uncertainties here refers to relative expandeduncertainly with a 95 percent confidence interval, normallywith a coverage factor k = 2. If manufacturer’s specificationdoes not specify uncertainty as stated above, then manufacturersshould be contacted for proper conversion.

11 TEST METHODS FOR TOTAL LUMINOUSFLUX MEASUREMENT

11.1 The total luminous flux (lumen) of SSL productsshall be measured with an integrating sphere systemof a goniophotometer. The method may be chosendepending on what other measurement quantities,namely colour, intensity distribution, etc, need to bemeasured, the size of SSL products, and otherrequirements. Some guidance on the use of eachmethod is given below.

11.1.1 Integrating Sphere System

The integrating sphere system is suited for totalluminous flux and color measurement of integratedLED lamps and relatively small size LED luminaires(see 11.2.2) for the guidance on the size of SSLproducts that can be measured in an integrating sphereof a given size. The integrating sphere system has theadvantage of fast measurement and does not require adark room. Air movement is minimized andtemperature within the sphere is not subject to thefluctuations potentially present in a temperature

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IS 16106 : 2012

controlled room. It should be noted that heat from theSSL product mounted in or on the integrating spheremay accumulate to increase the ambient temperatureof the product under test (see 11.2.1).

Two types of integrating sphere systems are used oneemploying a V (λ) corrected photometer head (see11.3), and another employing a spectroradiometer asthe detector (see 11.2). Spectral mismatch errors (see11.3.6) occur with the first method due to the deviationof the relative spectral responsivity of the integratingsphere photometer form the V (λ), while there aretheoretically no spectral mismatch errors with thesecond method. The spectroradiometer method ispreferred for measurement of SSL products becausespectral mismatch errors with the photometer head(see 3.9) tend to be significant for LED emissions andcorrection is not trivial, requiring knowledge of thesystem spectral responsivity as well as the spectrumof the device under test. In addition, with thespectroradiometer method, colour quantities can bemeasured at the same time as total luminous flux.Further descriptions on both the methods are givenin 11.2 and 11.3.

11.1.2 Goniophotometer

Goniophotometers provide measurement of luminousintensity distribution as well as total luminous flux.Goniophotometer can measure total luminous flux ofSSL products of relatively large size (correspondingto dimensions of traditional fluorescent lampluminaires) while they can measure small SSL productsas well. A goniophotometer is installed in a darkroom,normally temperature controlled, and is not subject toheat accumulation from a source being measured. Careshall be taken, however, for drafts from ventilation thatmight affect measurement of SSL products that aresensitive to temperature. The ambient temperature mustbe measured and maintained as specified in 4.2.Measurements with a goniophotometer are timeconsuming compared to a sphere photometer.Goniophotometers using broadband photopic detectorsare susceptible to the spectral mismatch errors notedabove. In fact, correction for spectral mismatch can bemore difficult if there is significant variation in colourwith angle. The use of goniophotometers formeasurement of SSL products are give in 11.4.

11.2 Integrating Sphere with a Spectroradiometer(Sphere Spectroradiometer System)

This type of instrument measures total spectral radiantflux (W/nm), from which total luminous flux andcolour quantities are calculated. By using an arrayspectroradiometer, the measurement speed can be ofthe same magnitude as for a photometer head.

11.2.1 Integrating Sphere

The size of the integrating sphere should be large enoughto ensure that the measurement errors due to effects ofbaffle and self-absorption (see 11.2.5) by the test SSLproduct are not significant. The guidance on the size ofthe sphere required relative to the size of the SSLproducts to be measured is given in 11.2.2. In general,sphere size of 1 m or larger is typically used for compactlamps (size of typical incandescent and compactfluorescent lamps), and 1.5 m or larger of larger lamps(for example size of 4 foot linear fluorescent lamps andHID lamps). The sphere should also be large enough toavoid excessive temperature increase die to heat fromthe light source being measured. Two metre or largerspheres are typically used for measurement of lightsources of 500 W of larger.

The integrating sphere shall be equipped with anauxiliary lamp for self-absorption measurement(see 11.2.5). The auxiliary lamp for a spherespectroradiometer system must emit broadbandradiation over the entire spectral range of thespectroradiometer. Thus, a quartz halogen lamp istypically used for this purpose. The auxiliary lamp lightoutput needs to be stable throughout all the self-absorption measurements.

An interior coating reflectance of 90 percent to 98 percentis recommended for the sphere wall, depending on thesphere size and usage of the sphere. A higher reflectanceis advantageous for higher signal obtained and smallererrors associated with spatial non- uniformity of sphereresponse and intensity distribution variations of the SSLproducts measured. Higher reflectance is preferredparticularly for a sphere spectroradiometer system toensure sufficient signal-to-noise ratios in the entire visibleregion. It should be noted, however, that, with higherreflectance, the sphere responsivity becomes moresensitive to self-absorption effects and long-terms drift,and also, there will be more variation in spectralthroughput. If there is an opening in the sphere, theaverage reflectance should be considered, and highercoating reflectance will be advantageous to compensatefor the decrease of average reflectance.

11.2.2 Sphere Geometry

Figure 1 shows recommended sphere geometries of asphere-spectroradiometer system for total luminousflux measurement of SSL products. The referencestandards are for total spectral radiant flux. The 4πgeometry (a) is recommended for all types of SSLproduct including those emitting light in all directions(4 πsr) or only in a forward direction (regardless oforientation). The 2π geometry (b) is acceptable for SSLproducts emitting light only in forward direction(regardless of orientation), and may be used for SSL

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products having a large housing or fixture that are tolarge to use the 4π geometry. In either geometry, thesize of the SSL product under test should be limitedfor a given size of the sphere to ensure sufficient spatialuniformity of light integration and accurate correctionfor self-absorption. For measurement of integratedLED lamps, the sphere may be equipped with a lampholder with a screw-base socket.

In the 4π geometry, as a guideline, the total surfacearea of the SSL product should be less the 2 percent ofthe total area of the sphere wall. This corresponds to,for example, a spherical object of less than 30 cmdiameter in a 2 m integrating sphere. The longestphysical dimension of a linear product should be lessthan 2/3 of the diameter of the sphere.

In the 2π geometry, the opening diameter to mount aSSL product should be less than 1/3 of the diameter ofsphere. The SSL product shall be mounted within thecircular opening and in such a way that its front edgesare flush with the edges of the opening (or it can beslightly inside the sphere to ensure that all emitted lightis caught in the sphere). In this case, the gaps betweenthe edges of the opening and SSL product (or referencestandard) can be covered with a surface ( inner side iswhite ) in order that the measurement can be made in aroom with normal ambient lighting as the sphere iscompletely shielded from outside [see Fig. 2 (a)]. Ifthis is not convenient and the gaps are to be kept open,a darkroom arrangement (around the opening, at least)may be necessary so that no external light or reflectance

light enters the sphere [see Fig. 2 (b)]. In either case,the SSL product under test should be mounted to thesphere so that support material or structure does notconduct the heat from the SSL product to the spherewall (see also 4.3).

In either geometry, the size of the baffle should be as smallas possible to shield the detector port from direct illuminationfrom the largest test SSL product to be measured or thestandard lamp. It is recommended that the baffle is locatedat 1/3 to 1/2 of the radius of the sphere from the detectorport. The auxiliary lamp should have a shield so that its directlight does not hit any parts of SSL products under test or thedetector port.

Standard lamps for total spectral radiant flux are normallyquartz-halogen incandescent lamps that have broadbandspectrum to calibrate the spectroradiometer for the entirevisible region. For the 2π geometry, standard lampshaving only forward distribution are required. Forexample, a quartz-halogen lamp with a reflectorproviding appropriate intensity distribution may be usedas a reference standard source. For the 4π geometry,standard lamps having omni-directional intensitydistribution are commonly used but standard lampshaving forward intensity distribution also be needed.

It should be noted that integrating spheres do not haveperfectly uniform responsivity over their internalsphere surfaces. The sphere responsivity tends to beslightly lower for the lower half of the sphere due tocontamination by falling dust and also around the

All dimensions in millimetres.

FIG. 1 RECOMMENDED SPHERE GEOMETRIES FOR TOTAL LUMINOUS FLUX MEASUREMENT

USING A SPECTRORADIOMETER: (A) FOR ALL TYPES OF SSL PRODUCTS,(B) FOR SSL PRODUCTS HAVING ONLY FORWARD EMISSION

b

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sphere seams where small gaps exist. Therefore, if asphere (4π geometry) is calibrated with an omni-directional standard lamp and measures an SSL producthaving downward intensity distributions, the luminousflux tends to be measured slightly lower than it is. Thiserror tends to be more prominent for light sourceshaving narrow beam distributions. The magnitude oferrors depends on how well the sphere is designed andmaintained, and will be cancelled, if the angularintensity distributions of the standard lamp and the testSSL products are the same. To ensure that this error isnot significant, standard lamps having differentintensity distributions (omni-direction, downward/broad, downward/narrow) may be prepared and chosenfor the type of SSL products to be measured. Or, ifonly omni-directional standard lamps are used,correction factors should be established and appliedwhen SSL products having different intensitydistributions are measured. Such correction factors maybe established by measuring lamps or SSL productshaving different intensity distributions calibrated fortotal luminous flux using other accurate means (forexample, calibration traceable to National Standard,or using well-designed goniphotometer).

The ambient temperature in a sphere shall be monitoredaccording to 4.2. A temperature probe is often mountedbehind the baffle that shields the detector port fromthe light source if the baffle is mounted at the sameheight as the centre of the sphere [see Fig.1 (a)]. Whena SSL products is mounted on the sphere wall [see Fig.1(b)], the ambient temperature shall be measured behindthe baffle (side of spectroradiometer) in the sphere, inaddition to the ambient air outside the sphere near theproduct (see 4.2). Both readings must meet therequirement of 25 ± 1°C requirement.

If the ambient temperature in the closed sphere exceeds25 ± 1°C due to the heat generated by the SSL productunder test, the SSL product may be stabilized with thesphere partially open to achieve the required ambienttemperature within 25 ± 1°C until measurement is madewith the sphere closed. When measurement is taken,the sphere shall be closed gently to avoid air movementinside the sphere.

NOTES

1 The light output of incandescent standard lamps changes iftheir burning position is changed.

2 If the stability of the flux output of the product is monitoredwith the sphere photometer when the sphere is open, the roomlights shall be turned off and the position of open hemispheresshould not be moved.

11.2.3 Principle of Measurement

The instrument (integrating sphere plusspectroradiometer) must be calibrated against areference standard calibrated for total spectral radiantflux. Since the integrating sphere is included in thiscalibration, the spectral throughput of the sphere neednot be known. The total spectral radiant flux φTEST(λ)of a SSL product under test is obtained by comparisonto that of a reference standard φREF(λ):

φTEST

(λ) = i iTESTREF

REF

( ) 1( )

( ) ( )

y

y

ll

l a lf …(1)

Where yTEST(λ) and yREF (λ) are the spectroradiometerreadings for SSL product under test and for referencestandard, respectively, and α (λ) is the self absorptionfactor (see 11.2.5).

From the measured total spectral radiant flux φTEST

(λ) [W/nm], the total luminous flux φTest [lm] is

FIG. 2 MOUNTING CONDITIONS OF THE SSL PRODUCT UNDER TEST

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obtained by :

φTEST = Km lfÚ TEST (λ) V (λ)dλ ...(2)

where

Km = 683 lm/W

11.2.4 Spectroradiometer

Either mechanical scanning type or array typespectroradiometers may be used. The arrayspectroradiometer has the advantage of shortermeasurement time due to the multiplex nature of arrays.The spectroradiometer shall have a minimum spectralrange from 380 nm to 780 nm. The defined visiblespectral region is 360 nm to 830 nm2.

The detector port of the integrating sphere shall be aflat diffuser or a satellite sphere (a very smallintegrating sphere-detector systems with an opening)mounted flush to the sphere coating surface, so thatthe input of the sepctroradiometer at the detector porthas an approximate cosine response with be directionalresponse index f2 being less than 15 percent. It shouldbe noted that an optical fibre input (with no additionaloptics), often provided with array spectroradiometer,has a narrow acceptance angle and should not be usedwithout additional optics for cosine correction.

Calibrated spectroradiometer measure photometricquantities without spectral mismatch errors; however,there remain many other sources of error associatedwith spectroradiometer.

Errors can be significant when the spectral distributionof a test SSL product is dissimilar to the standard source(tungsten source). Major sources of error includebandwidth, scanning interval, wavelength accuracy,spectral stray light, detector non-linearity, and inputgeometry. For accurate colorimetry, a bandwidth andscanning interval of 5 nm or smaller are required forspectroradiometer methods.

NOTE — Errors in some poor quality array spectroradiometerscan be larger than high quality photometer heads.

11.2.5 Self Absorption Correction

Self absorption is the effect, in which the responsivityof the sphere system changes due to absorption of lightby the lamp itself in the sphere. Errors can occur, if thesize and shape of the test light source is different fromthose of the standard light source. The self absorptioncorrection is critical, since the physical size and shapeof the SSL products under test are typically verydifferent from the reference standard size and shape.The self absorption is wavelength dependent becausethe spectral reflectance of the sphere coating is notspectrally flat. The self absorption factor is given by :

α(λ) = aux, TEST

aux, REF

( )

( )

y

y

ll

…(3)

Where y aux, TEST(λ) and y aux, REF

(λ) are the spectroradio-meter readings for the auxiliary lamp when the SSLproduct under test or the reference total spectral radiantstandard, respectively, are mounted in or on the sphere(4π or 2π geometry). In this case, the SSL product andthe reference standard are not operated. Only theauxiliary lamp is operated.

11.2.6 Calibration

The instrument (integrating sphere plusspectroradiometer) shall be calibrated against totalspectral radiant flux standards traceable to NationalPhysical Laboratory (NPL).

11.3 Integrating Sphere with a Photometer Head(Sphere Photometer System)

This method is a traditional approach of integratingsphere photometry, using a photometer head as thedetector for an integrating sphere. This method isacceptable but less preferred due to the potential forlarge spectral mismatch errors in the measurement ofluminous flux of SSL products (if the mismatchcorrections are not applied) and also due to a need forseparate measurement instruments for colourquantities.

11.3.1 Integrating Sphere

Descriptions given in 11.2.1, also apply to this method,except for a difference in the requirement of auxiliarylamp. For a sphere-photometer system, the auxiliarylamp does not have to be limited to incandescent lamps.Rather, it is advantageous to use an auxiliary lamp thathas a spectral distribution similar to those of the SSLproducts typically measured, so that self absorption ismeasured accurately especially when the selfabsorption is very large (α < 0.8) or when the housingof SSL product under test is large and stronglycoloured. The auxiliary lamp needs to be stablethroughout the self absorption measurement of all SSLproducts under test. A stable white LED source, forexample, may be used.

11.3.2 Sphere Geometry

The recommended integrating sphere geometries forthis method are shown in Fig. 3. The difference fromFig. 1 is that a photometer head is used as the detector.The recommendations and requirements using these4π and 2π geometries are given in 11.2.2. All thedescriptions in 11.2.2 apply for this method exceptdifferences in the requirements of reference standardlamp.

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IS 16106 : 2012

The reference standard lamps are assigned totalluminous flux, and the same requirements as given in11.2.2 on the different intensity distributions apply. Forexample, for a narrow beam SSL product, standardlamps having similar narrow beam intensitydistribution should be used. If only omni-directionalstandard lamps are used, correction factors should beestablished for different types of intensity distribution.

While reference standards are traditionallyincandescent lamps, they do not have to be limited toincandescent lamps for a sphere-photometer system.Stable and reproducible SSL product (for example,using temperature-controlled white LED sources) maybe used as a reference standard of total luminous flux.It is advantageous, in reducing spectral mismatcherrors, to have the spectral distribution of the referencestandard to be similar to that of typical SSL productmeasured. Using SSL products as a reference standardmay also be advantageous in achieving angularintensity distribution similar to those of the SSLproducts to be measured.

11.3.3 Principle of Measurement

The total luminous flux of the test device is obtainedby comparison to that of a reference standard:

Φ TEST = i iTESTREF

REF

y F

y af …(4)

Where Φ REF is the total luminous flux (lumen) of thereference standard, y TEST and y REF are the photometer

signals for SSL product under test and for referencestandard, respectively. F is the spectral mismatchcorrection factor (see 11.3.6) and α is the selfabsorption factor (see 11.3.5). If factor F is notdetermined, F=1 should be used and the resultinguncertainty should be considered.

11.3.4 Photometer Head

The photometer head (see 3.9) shall have relativespectral responsivity well matched to the V (λ) function,while the spectral throughput of the sphere also effectsthe total spectral responsivity. The ′1f value of the totalsphere system (photometer head plus integratingsphere) shall be less than 3 percent. To further reduceuncertainty of measurements, a spectral mismatchcorrection may be applied. The procedures fordetermining ′1f value and spectral mismatch correctionfactor are given in 11.3.6.

The photometer head shall have an approximate cosineresponse with the ƒ2 (value)10 (directional responseindex) of less than 15 percent and the diffuser surfaceshall be mounted flush to the sphere coating surface.If a satellite sphere is used for cosine response, itsopening shall not be recessed; the opening edges ofthe satellite sphere shall be flush to the integratingsphere coating surface.

11.3.5 Self Absorption Correction

A self absorption correction shall be applied unlesstest SSL product and luminous flux reference standardare of the same model and same size (strict

FIG. 3 RECOMMENDED SPHERE GEOMETRIES FOR TOTAL LUMINOUS FLUX MEASUREMENT

USING A PHOTOMETER HEAD: (A) FOR ALL TYPES OF SSL PRODUCTS,(B) FOR SSL PRODUCTS HAVING ONLY FORWARD EMISSION

(a) 4πππππ Geometry (b) 2πππππ Geometry

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IS 16106 : 2012

substitution). The self absorption factor can bemeasured by :

α = aux, TEST

aux, REF

y

y…. (5)

Where yaux, TEST and yaux, REF are the photometer signalsfor the auxiliary lamp when the SSL product undertest or the total luminous flux reference standard,respectively, is mounted in or on the sphere (4π or 2πgeometry). They are not operated; only the auxiliarylamp is operated. The auxiliary lamp can be a halogenor incandescent lamp or a white LED source.

11.3.6 Determination of ′1f and Spectral MismatchCorrection Factor

The spectral responsivity of the integrating spherephotometer cannot be perfectly matched to the V (λ)function. An error (called spectral mismatch error)occurs when a test SSL product has a different spectralpower distribution from that of the standard source.The ′1f (value)10 is an index that indicates the degreeof mismatch in spectral responsivity, and the value ( inpercentage ) gives a rough indication of the magnitudeof errors that can occur for general white light sources,but errors can be larger than the ′1f value for SSLproducts consisting of only a few narrowbandemissions.

To determine ′1f value, the relative spectralresponsivity of the total sphere system s rel (λ) must beobtained. s rel (λ) is given as a product of relativespectral responsivity of the photometer head s ph, rel(λ)and the relative spectral throughput of the sphere Trel

(λ):

srel (λ) = sph, rel(λ) Trel (λ) …(6)

The s ph, rel(λ) shall be measured in hemisphericalillumination geometry. If it is measured only in normaldirection, uncertainty shall be determined. Trel (λ) istheoretically given by

Trel (λ) = a

a

( )

1 ( )k

l∑

- lr

r…(7)

Where ρa (λ) is the average reflectance of the entireinner sphere surface (including ρ = 0 for an opening,if there is one) and k is a normalization factor. If ρa (λ)of the integrating sphere in use is measured accurately,Trel (λ) may be obtained using this equation. However,integrating spheres in use are more or less contaminatedand the data of coating samples tend to deviate fromthe reflectance of the real sphere surface. Therefore, itis recommended that Trel (λ) be directly measured onthe integrating sphere.

Once Srel (λ) is determined, ′1f is calculated by

′1f =*

rel ( ) ( ) d100% with

( ) d

s V

V

l

l

l - l l¥

l lÚ

Ú

s*rel (λ) =

A

relrelA

( ) ( )d( )

( ) ( ) dS

S Vs

S

l

l

l l l∑ l

l l lÚÚ

…(8)

Where SA (λ) is spectral distribution of CIE illuminantA and V (λ) is the spectral luminous efficiency function.With knowledge of rel ( )s l and the relative spectral powerdistribution S TEST (λ) of the SSL product under test, thespectral mismatch correction factor F is given by:

F = REF rel TEST

REF TEST rel

( ) ( )d ( ) ( )d

( ) ( ) d ( ) ( ) d

S s S V

S V S s

l l

l l

l l l l l l

l l l l l lÚ Ú

Ú Ú…(9)

Where SREF (λ) is the spectral distribution of thereference standard source. Spectral mismatch errorscan be corrected by multiplying the factor F to themeasured lumen value of the SSL product. Theaccuracy of S TEST (λ) is generally not very critical,and thus, the nominal spectral distribution of a productmay be used.

11.3.7 Calibration

The integrating sphere photometer shall be calibratedagainst total luminous flux standards traceable tonational standards.

11.4 Goniophotometer

Goniophotometer are normally used for measurementof luminous intensity distribution, from which totalluminous flux can be obtained.

11.4.1 Type of Goniometer

Goniophotometer shall be the type that maintains theburning position unchanged with respect to gravity;therefore, only Type C goniophotometer are allowable.Type C goniophotometers include moving detectorgoniophotometers and moving mirrorgoniophothometers. Care should be exercised toprevent light reflected from the mechanical structureof the goniophotometer or any other surface includingsecondary reflections from surfaces of the SSL productitself from reaching the photo detector. The speed ofrotation of the positioning equipment should be suchthat it minimizes the disturbance of the thermalequilibrium of the SSL product.

11.4.2 Principle of Total Luminous Flux Measurement

By measuring the luminous intensity distributionI (θ, Φ) of the source, the total luminous flux isobtained by;

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IS 16106 : 2012

Φ =2

0 0( , )sin d dI

p p

= =Ú Úf fq f q q f …(10)

If the photometer head is calibrated for measuringilluminance E (θ, Φ),

Φ =2

2

0 0( , ) sin d dr E

p p

= =Ú Úf qq f q q f …(11)

Where r is the rotation radius of the reference plane ofthe photometer head. A sufficiently long photometricdistance, r, is required for measurement of luminousintensity distribution (see 11.4.1).

The distance requirement is not critical if only totalluminous flux is to be measured. As indicated byequation (11), as long as the illuminance is measuredaccurately, the total luminous flux can be measuredaccurately even with a relatively short photometricdistance (radius r), thus less space for thegoniophotometer is required for a given size of lightsource to be measured. In this case, the detector musthave cosine corrected angular responsivity within itsfield of view for the test SSL product. By definitiongiven in equation (11), the location of the light sourcerelative to the rotation center is theoretically notrelevant, and therefore, the alignment of light sourceis not critical for measurement of total luminous flux.

11.4.3 Scanning Resolution

Scanning resolution fine enough to accurately definethe test sample shall be used. For typical wide-angle,smooth intensity distributions, a 22.5° lateral(horizontal) and 5° longitudinal (vertical) grids maybe acceptable. Finer angle resolution (smaller testincrements) shall be used where the luminous intensityfrom the SSL product is changing rapidly or is erratic,such as in beam forming sources.

11.4.4 Angle Coverage

The range of the angular scan must cover the entiresolid angle to which the SSL product emits light. Adisadvantage of a goniophotometer, when measuringtotal luminous flux, is that a goniophotometer ingeneral has some angular region where emission froma light source under test is blocked by its mechanism(for example, an arm for SSL product holder) so thatmeasurement in that direction cannot be made ( suchangle is called dead angle). This is not a problem forSSL products that emit light only in the forwarddirection similar to many existing fixtures. However,this can be a problem for SSL product that emits lightin all directions (for example, integrated LED lampssimilar to compact fluorescent lamps).Goniophotometers with a large dead angle are notsuited for total flux measurement of such SSL products.

If the dead angle is small (for example, ±10° or less),it is possible to interpolate the missing data points withan additional uncertainty.

11.4.5 Polarization

It should be noted that mirror type goniophotometershave a detection system that is polarization sensitivedue to the slightly polarizing characteristics of mirrorsthemselves. Sensitivity to polarized light can causesignificant errors when measuring the total luminousflux of SSL products that emit polarized light. Formeasurement of such SSL products, goniophotometersthat do not use a mirror are recommended. Some mirrortype goniophotometers have an option to mount aphotometer head directly on the rotating arm for suchpurposes.

11.4.6 Photometer Head

The photometer head of the goniophotometer shallhave relative spectral responsivity matched to the V (λ)function. The ′1f (value)10 of the spectral responsivityshall be less than 3 percent. It is further desirable toapply spectral mismatch corrections for the photometerreading. For determination of ′1f and spectral mismatchcorrection factor, see equations (8) and (9), with srel (λ)being the relative spectral responsivity of thephotometer head, measured in normal direction.

For the total luminous flux measurement describedin 11.4.2, the photometer head shall have good cosineresponse within the angle range where light is incident,with the ƒ2 (ε,Φ) value (relative deviation from thecosine function)10 of less than 2 percent within theacceptance angle range. The field-of-view of thephotometer head shall be limited (for example, usingaperture screens ) in order to shield stray light reflectedfrom the angles other than from the light source beingmeasured. To minimize stray light errors within thefield-of-view of the photometer, it is recommended touse a light trap on the other side of the detector armand/or use low reflectance material ( such as blackvelvet ) for the wall and floor surfaces.

11.4.7 Calibration

The goniophotometers for measuring luminousintensity distribution shall be calibrated against theilluminance or luminous intensity standard traceableto national standards. In addition, goniophotometersfor measuring total luminous flux shall be validatedby measurement of total luminous flux standard lampstraceable to national standards. Such validationmeasurements shall use standard lamps having similarangular intensity distributions (directional/omni-directional) as the type of SSL products to be testedwith the goniophotometer.

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IS 16106 : 2012

12 LUMINOUS INTENSITY DISTRIBUTION

The recommendations given in 11.4 pertain togoniophotometers used to measure luminous intensitydistribution as well as total luminous flux. Formeasurement of luminous intensity distribution, asufficient photometric distance shall be used, generally,more than five times of the largest dimension of thetest SSL product having broad angular distributions.A longer distance may be needed for narrow beamsources.

The coordinates system and geometry for mountingSSL products should follow the practice used intraditional luminaire testing in specific applications.The absolute luminous intensity distribution ofmeasured SSL products shall be reported.

Electronic data of measured luminous intensitydistributions, if necessary, shall be prepared forabsolute photometry in an electronic data format byspecifiers and designers to reliably predict illuminancelevels in design applications. The data, however, shallbe used with the understanding that the photometricresult describes the performance of a single luminaireand does not necessarily represent the averageperformance of a group of the same SSL luminaires.

NOTE — The presentation of normalized luminous intensitydata using the relative photometry method, commonly used intraditional luminaire testing, cannot be used for SSLproduction.

13 LUMINOUS EFFICACY

The luminous efficacy (lm/W) of the SSL product, ηv,

is given as the quotient of measured total luminous fluxΦTEST (lumen) and the measured electrical input powerP TEST (watt) of the SSL product under test as

ηv = [ ]TEST

TEST

/lm WP

q…(12)

NOTE — The luminous efficacy described above is luminousefficacy of a source. It should not be confused with luminousefficacy of radiation, which is the ratio of luminous flux (lumen)to radiant flux (watt) of the source.

14 TEST METHODS FOR COLOURCHARACTERISTICS OF SSL PRODUCTS

The colour characteristics of SSL products includechromaticity coordinates, correlated colourtemperature, and colour rendering index. Thesecharacteristics of SSL products may be spatially non-uniform, and thus, in order that they can be specifiedaccurately, the colour quantities shall be measured asvalues that are spatially averaged, weighted to intensity,over the angular range where light is intentionallyemitted from the SSL product.

14.1 Method Using a Sphere SpectroradiometerSystem

The first recommended method to achieve this is tomeasure total spectral radiant flux using a sphere-spectroradiometer system as descried in 11.2. Themeasured total spectral radiant flux is a spatiallyintegrated quantity, thus colour characteristicscalculated from this are already spatially averaged. Themethod given in 11.2 to perform measurements shallbe followed.

14.2 Method Using a Spectroradiometer of ColorimeterSpatially Scanned

This method may be used when a sphere-spectroradiometer system is not available, or when thetest sample is too large to be measured with a sphere-spectroradiometer system. This method uses aspectroradiometer and/or a colorimeter that measuresthe chromaticity of the SSL products under test indifferent directions. This can be achieved mostefficiently by mounting the colour-measuringinstrument on a goniometer (called gonio-spectroradiometer, or gonio-colorimeter). Theluminous intensity distribution and chromaticitycoordinates can be measured at the same time, takingreadings at appropriate angle intervals (see 11.4.3) overthe entire angle range where the light is intentionallyemitted from the product. Then, the spatially averagedchromaticity is obtained from all measured points usingequation (13), or based on spatially integratedtristimulus values.

If a gonio-spectroradiometer or gonio-colorimeter isnot available, this can also be achieved by manuallypositioning the instrument for given directions at aconstant distance, as the angle accuracy is not verycritical in this measurement. The chromaticitycoordinates and luminous intensity (or illuminance )shall be measured at 10° or less intervals for verticalangle θ over the angle range where light is intentionallyemitted from the source and at minimum two horizontalangles Φ = 0° and 90° (see Fig. 4). The chromaticitymeasurements need to be made only for the θ angleswhere the average luminous intensity is more than10 percent of the peak intensity. The averagechromaticity coordinates (x, y) or (u', v) shall beobtained as a weighted mean of all measured points,weighted by the illuminance and the solid angle factorat each point as Fig. 4.

The chromaticity coordinates and luminous intensityfor Φ = 0° and Φ = 90° (or more Φ angles) are firstaveraged at each θ angle and expressed as x (θi), y(θi)and I(θi) where θi = 0°, 10°, 20°,….,180°. Then theaverage chromaticity coordinates xa is calculated as aweighted mean:

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IS 16106 : 2012

FIG. 4 GEOMETRY FOR THE CHROMATICITY MEASUREMENT USING A GONIOMETER (THE FIGURE SHOWS

THE CASE FOR A SSL PRODUCT EMITTING LIGHT IN DOWNWARD DIRECTIONS ONLY)

xa = ii

19i i

i i i i i 191

i i=1

( ), ( )( ) ( ) with ( ) =

( ) ( )i

i

Ix w w

I=Â

Âq W q

q q qq W q

…(13)

and

i i i

i i ii

i i i

2 [cos( ) cos( )]; for 02

2 [cos( ) cos( )]; for( ) 2 2

10 , 20 , 170

2 [cos( ) cos( )]; for 1802

DÏ - + = ∞ÔÔ

D DÔ + - +Ô= ÌÔ = ∞ ∞ º ∞Ô

DÔ + - = ∞ÔÓ

qp q q q

q qp q q q

W q

qp q q q

∆θ = 10°

Chromaticity coordinates ya and other average colourquantities are calculated similarly. This formula is anapproximation but provides sufficient accuracy forpractical applications. Rigorously, the spatiallyintegrated colour quantities are calculated from thegeometrically-total flux of the tristimulus values X,Y, Z.

If a tristimulus colorimeter is used, it should becalibrated against the test SSL product by comparisonwith a spectroradiometer, or it should measure onlycolour differences from a reference point (for example,perpendicular direction), and the chromaticity of thereference point should be measured with a

spectroradiometer so that absolute chromaticities at allthe points are obtained based on the spectroradiometerreading. The photometric output (illuminance) alsoneeds to be recorded to calculate the weighted averagedescribed above. For this colour uniformitymeasurement the distance shall be more than 5 timesthe largest dimension of the light emitting area of theproduct under test.

If the spatial non-uniformity of colour of a givenproduct has been determined to be negligibly small(∆u'v' ≤ 0.001, see 14.5), the average chromaticityof the product of the same model can be measuredin one direction near the peak of its intensitydistribution.

The spectroradiometer used in this measurement(see 14.2) shall be calibrated against spectral irradianceor spectral radiance standards traceable to a nationalmetrology institute.

14.3 Spectroradiometer Parameters ImpactingMeasured Colour Characteristics

The spectroradiometer shall have a minimum spectralrange of 380 nm to 780 nm. The spectroradiometerused in either methods (see 14.1 or 14.2) shall beselected and set up so that the relative spectraldistribution is measured accurately even for SSLproduction having narrowband spectral distributions.The bandwidth and scanning intervals are amongimportant parameters for measurement of spectral

13

IS 16106 : 2012

distributions of light sources in general. The bandwidthand wavelength scanning intervals shall be 5 nm orsmaller (unless appropriate correction methods areapplied) and should be matched unless wavelengthintervals are very small (for examaple, 1nm or less).

14.4 Colorimetric Calculations

The chromaticity (x,y) and / or (u',v',) and correlatedcolour temperature (CCT, unit: Kelvin) are calculatedfrom the relative spectral distribution of the SSLproduct. CCT is defined as the temperature of aplanckian radiator having the chromaticity nearest thechromaticity of the light source on the (u', 2/3 v')chromaticity diagram. The colour rendering index(CRI) is calculated according to the formulae definedin IS 3646 (Part 1).

14.5 Spatial Non-uniformity of Chromaticity

SSL products may have variation of colour with angleof emission. Spatial non-uniformity of chromaticityshall be evaluated using the measurement conditionsdescribed in 14.2. The spatial distribution ofchromaticity coordinates of the SSL products aremeasured at two vertical planes (Φ = 0°, Φ = 90°) andthe spatially averaged chromaticity coordinate iscalculated from these points according to equation(13).

The spatial non-uniformly of chromaticity, ∆u'v' isdetermined as the maximum deviation [distance on theCIE (u', v') diagram] among all measured points fromthe spatially averaged chromaticity coordinate. For thisevaluation, accuracy only in chromaticity differencesis critical, and thus, all measurements may be madewith a tristimulus colorimeter if a spectroradiometeris not available.

15 UNCERTAINTY STATEMENT

Statement of uncertainty if required may be providedby the testing authority. For all photometricmeasurements, expanded uncertainty with a confidenceinterval of 95 percent shall be applied which in mostcases use a coverage factor of k = 2.

16 TEST REPORT

The test report shall list all significant data for eachSSL product tested together with performance data.The report shall also list all pertinent data concerningconditions of testing, type of equipment, SSL products

and reference standards. Typical items reported are:

a) Date and name of the testing agency;b) Manufacturer’s name and designation of SSL

product under test;

c) Measurement quantities measured (totalluminous flux, luminous efficacy, etc);

d) Rated electrical values [clarify a.c.(frequency) or d.c.] and nominal CCT of theSSL product tested;

e) Number of hours operated prior tomeasurement (0 h for rating new products);

f) Total operating time of the product formeasurement including stabilization;

g) Ambient temperature;h) Orientation ( burning position ) of SSL

product during test;

j) Stabilization time;

k) Photometric method or instrument used(sphere photometer, sphere spectroradio-meter, or goniophotometer);

m) Designation and type of reference standardused (wattage, lamp type, intensity distributiontype omni-directional/ directional) and itstraceability;

n) Correction factors applied (for example.,spectral mismatch, self absorption, intensitydistribution, etc);

p) Photometric measurement conditions (forsphere measurement, diameter of the sphere,coating reflectance, 4π or 2π geometry, forgoniophotometer, photometric distance);

q) Measured total luminous flux (lm) and inputvoltage (V), current (A), and power (W) ofeach SSL product;

r) Luminous intensity distribution (ifapplicable);

s) Colour quantities (chromaticity coordinates,CCT and/or CRI for white light products);

t) Spectral power distribution (if applicable);

u) Bandwidth of spectroradiometer, if spectraldistribution and/or colour quantities arereported;

v) Equipment used;

w) Statement of uncertainties ( if required ); and

y) Deviation from standard operatingprocedures, if any.

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IS 16106 : 2012

A-1 GENERAL

This Annex explains how the measurement of solidstate lighting (SSL) products differs from measurementof traditional lamps and luminaires, why this standardis needed, and why sampling is not addressed.

A-2 WHY SOLID STATE LIGHTING ISDIFFERENT

In photometric measurements of traditional lamps andluminaires, the operating conditions are differentdepending on the type of lamp. These operatingconditions include the reference ballast, electricalmeasurement, stabilization time, handling of lamp, andmore. Thus different standards were developed fordifferent lamp types and even luminaires that usemultiple lamp types. Standards for measurement ofSSL products are needed because LED source havedifferent requirements for operation and temperatureconditions than traditional light source.

SSL products can be in the form of lamps such asintegrated LED lamps, or luminaires, which range inscale from small lamps, to size of large fluorescentluminaires. Depending on the size and quantitiesneeded, these products may be measured in anintegrating sphere or a goniophotometer, thus SSLproducts are measured by lamp photometry engineersas well as by luminaire photometry engineers, havingdifferent practices and culture. This standard brings acommon basis and uniform measurement methods forboth groups of engineers.

Traditionally, photometric measurements have beenmade for lamps and for luminaires separately usingdifferent test methods. Lamps are typically measuredwith integrating spheres, and total luminous flux andchromaticity are the main quantities of interest.Luminaires are normally measured withgoniophotometers, and luminous intensity distributionand luminaire efficiency are the main quantities ofinterest, standards have been developed separately formeasurement of lamps, such as linear fluorescentlamps, incandescent lamps, and for compactfluorescent lamps and for measurement of luminaires.However, for must current SSL products, LED lampscannot be separated form luminaires, and the natureof SSL products resembles both light sources andluminaires Thus, none of the existing standards forlamps or luminaires are directly applicable to SSLproducts.

ANNEX A(Foreword)

COMPARISON OF METHOD OF MEASUREMENT OF SOLID STATE LIGHTING (SSL)PRODUCTS AND MEASUREMENT OF TRADITIONAL LAMPS AND LUMINAIRES

A-3 RELATIVE AND ABSOLUTE PHOTOMETRY

Traditional luminaire photometry methods do not workfor SSL products because traditionally, luminaries arenormally tested with a goniophotometer using aprocedure called relative photometry. In this method,a luminaire under test and the bare lamp(s) used in theluminaire are measured separately. Then the luminousintensity distribution data of the luminaire measuredwith the goniophotometer are normalized by themeasured total luminous flux of lamps used in thetested luminaire. Therefore, the luminous intensitydistribution is normally presented in relative scale (forexample, candela per 1 000 lumens). Such test methodscannot be used for SSL products because, in most SSLproducts, LED lamps sources are not designed to beseparated from the luminaire. Even if the LED sourcecan be separately and measured separately, the relativephotometry method will not work accurately becausethe light output of the LED source will changesignificantly if operated outside the luminaire due todifferences in thermal conditions. Therefore, existingstandards for measurement of luminaires cannot beused for SSL products.

SSL products should be measured using absolutephotometry method. However, absolute photometry israrely used for traditional luminaires and is notdescribed in sufficient detail in any standards. Clause11.4 of this standard describes detailed requirementsfor such absolute photometry for total luminous fluxmeasurement of SSL products.

A-4 SAMPLING

With the relative photometry method commonly usedfor luminaires, the results are independent fromindividual variations of lamp lumen output becauseof the normalization using the measured totalluminous flux of lamps. As a result, the individualvariation of lamp light output due to lamp variationand variation in the ballast factor of the control gearis removed.

Inconsistencies in luminous flux measurements as aresult of variation in luminaire geometry are normallyinsignificant when the inconsistencies due to variationsin the luminous flux produced by the lamp(s) areremoved. It should be noted that the variation inluminous flux provided by the lamp is function of boththe lamp(s) and their ballast control gear. As a result,it has been historically sufficient to measure only one

15

IS 16106 : 2012

sample for rating a luminaire product. This is thepractice often used in performance rating of luminaires.On the other hand, the results of measurement of SSLproducts are directly affected by the output of thesources, and are always subject to individual variationsof LED sources, which tend to be significantly largerthan even those of fluorescent lamps. Therefore,measurement of one sample is insufficient for ratingSSL products and appropriate sampling and averagingof results is required for SSL products. The tolerancerequirements for individual product variations may bedifferent for different applications. This standarddescribes test methods for individual SSL product anddoes not cover such sampling methods for ratingproducts, which should be covered by a regulatory

requirement, customer requirement of agencyrequirement.

A-5 FUTURE PROJECTION

This standard would be reviewed continuously keepingin pace with the innovation of new technology anddevelopments in the field of SSL products. In particular,measurement of luminaire characteristics usinggoniophotometry would be requiring further detailing.Requirements of luminaires differ for different lightingapplications, and it would therefore require substantialefforts to cover this area. This standard would beupgraded in due course as well as develop additionalstandards and methods needed for measurement of SSLproducts, if considered necessary.

Published by BIS, New Delhi

Bureau of Indian Standards

BIS is a statutory institution established under the Bureau of Indian Standards Act, 1986 to promoteharmonious development of the activities of standardization, marking and quality certification of goodsand attending to connected matters in the country.

Copyright

BIS has the copyright of all its publications. No part of these publications may be reproduced in any formwithout the prior permission in writing of BIS. This does not preclude the free use, in the course ofimplementing the standard, of necessary details, such as symbols and sizes, type or grade designations.Enquiries relating to copyright be addressed to the Director (Publications), BIS.

Review of Indian Standards

Amendments are issued to standards as the need arises on the basis of comments. Standards are also reviewedperiodically; a standard along with amendments is reaffirmed when such review indicates that no changes areneeded; if the review indicates that changes are needed, it is taken up for revision. Users of Indian Standardsshould ascertain that they are in possession of the latest amendments or edition by referring to the latest issue of‘BIS Catalogue’ and ‘Standards : Monthly Additions’.

This Indian Standard has been developed from Doc No.: ETD 23 (6310).

Amendments Issued Since Publication

Amend No. Date of Issue Text Affected

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