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PHOTOMETRIC LABORATORY

By investing in a modern full scale goniophotometric laboratory LIGMAN strengthens its test and measurement capacities and underlines its commitment to strengthening its in-house capacities for providing global markets with products of highest quality and modern design.

LMT GO-DS 2000 for the LIGMAN Design Center, Bangkok

The flagship of the new laboratory will be a goniophotometer with mirror arrangement, manufactured in Germany by LMT Lichtmesstechnik Berlin GmbH. The GO-DS model goniophotometer will provide highest quality data for LIGMAN's luminaire design and quality control experts, elevating LIGMAN's photometric capacities to a level shared by an elite circle of industry leaders around the World. Similar LMT systems are employed by internationally recognized metrology institutes and test houses such as METAS, Switzerland, NPL, Great Britain, VDE Germany, and KEMA/DEKRA, Netherlands as well.

LIGMAN selected the Berlin based manufacturer for its long-standing reputation as provider of high performance photometric equipment with a proven record for precision, robustness, and long-term reliability. The fully automatic GO-DS goniophotometer with mirror arrangement measures the luminous intensity distribution of luminaires according to the C-γ coordinate system, with which further photometric information can be calculated, including luminous flux, average luminance and glare values. All data can be exported into LIGMAN's luminaire design software for further evaluation and processing.

Measurements with the system are executed in accordance with a number of international, guidelines, most notably the [i]CIE Publication 121-1996, EN 13032-1:2004, and IES LM 79-08 2007.

Functional Principles

The luminous intensity distribution of a luminaire is determined by measuring its illuminance at a given distance in all possible directions in space. The LMT GO-DS goniphotometer has therefore two independent rotational axes. The goniophotometer consists of a rotating luminaire holder, a rotating mirror, and a fixed photometer. The measurement procedure is executed by rotating the luminaire around the mirror at a fixed radius, whereby the mirror deflects the light emitted by the test object towards a photometer.
By employment of a mirror the test objects can be positioned in such a way so that they remain in their designated burning position with respect to gravity throughout the test procedure. This is essential when testing light sources whose photometric performance is orientationally sensitive.

GO-DS Features
The mirror center of the LMT GO-DS always remains in the center of rotation producing a narrow and stable light cone. The photometer head can be positioned at any number of fixed distances depending on the requirements of the light sources. A number of fixed baffles are installed between the photometer head and the mirror to prevent stray-light.
Slip ring contacts allow for continual rotation of the test objects upon their vertical axis. Uninterrupted rotation of the test objects allows for rapid testing and prevents shocks to the luminaires caused by stop and go rotation.
Moreover the rotation speed can be variably selected, this is especially important when testing of luminaires with light sources which are highly sensitive to movement, e.g. for T5 fluorescent lamps and SSL products.

The GO-DS design with centrically rotating mirror enables compact laboratory design resulting in low facility investment and long-term low energy costs for air-conditioning.

Test Data Recording

During each measurement the computer records illuminance or luminous intensity, the corresponding angles of radiation, as well as electrical operational parameters of the measurands and saves this data for further evaluation. The individual test routines can be programmed by LIGMAN Engineers in the software interface. Luminous flux , scaled luminous intensity distribution (cd/klm), light output ratio, averaged luminance, glare as well as the chromaticity coordinates, correlated color temperature and color rendering index, spatially averaged, are calculated automatically. The measurement data are presented in tabular form and as polar diagrams in C -plane pairs portrayed opposite of each other. For importing data into commercial calculation programs such as RELUX, DIAlux, TunLight etc., the measurement data are recorded in numerous formats including CIE, CEN, EULUMDAT, IES, etc.

LED Testing Capabilities

LIGMAN will receive a system designed specifically to meet the challenges of goniophotometry and goniospectroradiometry for modern SSL products.

The GO-DS photometric system is adapted to the spectral responsivity of the human eye by means of LMT Mosaic Filtering®. This proprietary procedure enables LMT to produce a photometer attaining a match ≤ 1% even considering the spectral influence of the mirror. The unparalleled spectral match of the photometer makes the system ideal for testing LED light sources whose typically narrow band spectral distributions can cause considerable measurement errors when tested against conventional photometers.

The GO-DS at LIGMAN includes a specially designed array type spectroradiometric system for colorimetrics optimized with respect to speed and precision for employment with a mirror type goniophotometer. This fully automatic system is dedicated to testing the spatial uniformity of color quantities according to IES LM 79-08, a pre-requisite for qualifying SSL lighting products for the US Energy Star program.

Luminous Flux Measurements
While the absolute luminous flux of light sources can be tested on the GO-DS, for rapid testing of luminous flux of lamps and SSL modules in large numbers the substitution method in an integrating sphere is the method of choice. In this case the measurands are tested against standard light sources with similar geometric and photometric properties which have been calibrated according to the absolute method.

For this purpose LIGMAN has selected the LMT UL 2250/1650 model Integrating Sphere system.
The integrating sphere is specially configured in compact design allowing for testing of light sources up to 1.6m length. The outstanding characteristic of this instrument is the very low spectral throughput of the entire system of f1' ≤0.1%.

The German manufacturer achieves this by employment of a proprietary photometric coating (BaS,) with variation in uniformity of response in VIS range of <1.0% , in combination with an LMT Photometer employing LMT Mosaic Filtering®. This limits spectral mismatch indices to ≤2% when testing most any type of lamp including LEDs. This performance eliminates the need to work with spectral mismatch correction factors to compensate for uncertainties caused by different spectral distributions of standard lamp and measurand.

LMT will supply the sphere to LIGMAN with a special port and test bench for testing light sources in 2 pi orientation mounted to the exterior of the sphere. This test orientation is recommended for testing of forward emitting SSL lighting by the IES LM 79-08.

The test results including luminous flux, temperature and lamp stability over time, as well as electrical parameters are recorded by the integrated software and made available to LIGMAN engineers in recognized file formats for further evaluation.

Integrating Sphere Features
Manufacturer	LMT Lichtmesstechnik GmbH Berlin
Model	LMT UL 2250/1650 match ≤ 1%, including spectral influence of the mirror optimized for for SSL colorimetrics
Material	Full aluminum, CNC pressed hemispheres for uniformity, stability and achieving thermal equilibriums.
Spectral Throughput:	f1' ≤0.8% for photometer head and coating combined
Dynamic range	As low as 0.001 lm allowing for testing of widest range of light sources in same integrator
Test object Orientation	2 pi, 4 pi, pendant, horizontal, upright
Temperature Monitoring	Built-in sensor
Auxiliary lamp	Built-in quartz halogen
Max. Test object Length	1.6m

Mirror Goniophotometer Features
Manufacturer	LMT Lichtmesstechnik GmbH Berlin
Model Type	Type 3.1 according to EN 13032:2004/ Type C according to LM-75-01
Mirror	Oval, Tested for spectral and polarization characteristics as well as for flatness and reflective characteristics according to EN 13032-1:2004 Match ≤ 1%, including spectral influence of the mirror
Photometer Spectrometer	Optimized for for SSL colorimetrics
Rotational speed	Variable
Test object Orientation	Up to 2m dia. and 50kg pendent or upright, motorically adjustable with stable orientation during measurement
Measurementangles Stray-light	Selectable in 0.1° steps prevented with fixed baffles

Photometer Head with LMT Mosaic Filtering®.

UL 2250/1650 Integrating Sphere

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