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Technical Committee latest expert guidance and documents

• GN03 Measurement of the photometric performance of LED lighting

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Measurement of the photometric performance of LED lighting

ILP GD 3/16

May 2016

Allan HowardBEng(Hons) CEng FILP FSLL

Technical Director (Lighting)

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BACKGROUND3

Claims that special measurement instruments and processes are required for: LED light sources Measuring in the Mesopic range

That you can’t apply TR28 Measurement of road lighting performance on site BS EN 13201-4:2015 Methods of measuring lighting performance

GN3/16 clarifies the approach

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PANEL MEMBERS4

Teresa Goodman National Physical Laboratory Chair CIE TC2-65 Photometric measurements in the mesopic range

Peter Raynham University College London

Steve Fotios Sheffield University

Allan Howard WSP | Parsons Brinckerhoff

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WHY MEASURE?

Verification of compliance with performance specificationVerification of compliance with design expectationsLighting performance monitoring, maintenance reasonsLighting control / adaptive lighting, optimising energy savings Investigation of discrepancies between real conditions and

design expectations

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CORE REQUIREMENTS6

Only undertaken by those professionally qualified and competent in illuminating engineering

Must be aware of: Measurement Standards i.e. BS EN13201-4:2015 & TR 28 The properties and calibration of the instrument(s) Lighting installation design & measurement grids Health & safety requirements for safe working on site

- National Highway Sector Scheme Found 01 basic health & safety Test 04 Photometric performance testing

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MEASURING INSTRUMENT7

Illuminance measurement

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WHAT TO CONSIDER Quality

- Robust- Battery life- Short-term reproducibility- Portable

Consideration should be given to the viewing angle of the intended real-world receiver

When measuring illuminance on a surface we record all light falling in an arc of 180 degrees above the surface and 360 degrees around the sensor. The sensor must therefore be able to accurately capture light from all these directions

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THE SENSOR

Needs to reflect the response of the eye (CIE curve)Check sensor repose based upon supplier data sheet

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THE SENSOR

Not all sensors are the same

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CALIBRATION

Where measurements are to be used for contractual or legal performance measurements then the instrument(s) must be calibrated

Calibration Traceable to national standards such as those by ‘NIST’ or ‘NAMS’ and

manufacturers recommendations ISO 17025 accredited laboratory

Calibration frequency depends upon the frequency of use and how the instrument is treated, generally every 12 months is sufficient

An operation log should be maintained, thus if an instrument is found to be out of calibration its use can be tracked and past results checked

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HIGHWAY LIGHTING12

Standards based on Photopic levels (50 lux plus)Outdoor lighting levels – 50 lux down to 0.05 luxOperating in the Mesopic range

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HIGHWAY LIGHTING13

Mesopic illuminance lies between the Photopic and Scotopic levels

Position changes with adaption levelNo straight forward correlationCIE 191:2010

Defines the system to calculate Mesopic quantities Depends upon the:

- Photopic adaption luminance- S/P ratio of the adaption field

No agreed method for evaluating these adaption conditionsNot possible to take measurements of Mesopic illuminance

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CIE TC2-6514

Photometric measurements in the Mesopic rangeAwaiting research into the adaption field in respect to:

Size Shape Location Visual scene

Develop the adaption coefficient to be evaluatedEnable practical on-site measurement

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BS5489-1:201315

Choose the lighting class and light source

Where permitted apply the light source S/P ratio

Methodology described in PLG03

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TR2816

Measurement process set against design calculationsBased upon performance of the luminaire & light sourceProvides test / survey grids based upon design calculationsSurveys measure actual illuminance at measurement pointsCompared to calculated levelsDetermine the performance of the installation

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GN 3/1617

Standard photometer to be usedNo requirement to measure the S/P ratioNew installations with design dataExample:

Choose light class and source type Run design programme, use S/P ratio where permitted Design programme targets a lower illuminance based on class Lower illuminance values should be found on site.

Where S/P ratio is not applicable then use calculated values

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GN 3/16 - EXAMPLE18

Lighting class P2 Class average illuminace 10 lux

Light source Ra > 60S/P ratio 2.4Target average illuminace 7.3 luxOn site measurement expected to demonstrate 7.3 lux

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GN 3/1619

Existing installationNo design dateApplication of S/P ratio permittedMeasured illuminance to be reverse assessed based upon

manufacturers advised S/P ratioUse PLG03 to assign the appropriate lighting classWhere S/P ratio is not applicable (M Class) then use

measured values

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GN 3/16 - EXAMPLE20

Measured grid provides an average illuminance 7.3 luxS/P ratio permitted for Class of roadS/P ratio of 2.4Apply PLG03Demonstrates compliance with Class P2 (10 lux)

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UNCERTAINTIES21

Discussed in: TR28 CIE 194 BS EN 13201-4:2015

Need to be considered

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SUMMARY22

No special test instruments are requiredGN provides clear guidanceCompetency for those undertaking this workConsiderations for S/P ratio

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