EBV LightLab is offering at first glance the two integrating spheres with a diameter of 250 mm and 1000 mm, where the lighting current and the radiant power are measured
These measurements are necessary for determining the luminous efficiency (measured in lumens per watt). In addition, it is in these spheres that colorimetric measurements of the quantitative spectral distribution are performed and the colour temperature and colour rendering index are determined. The EBV LightLab contains two integrating spheres: a 2p sphere with a diameter of 250 mm and a 4p sphere with an internal diameter of 1,000 mm. The interior of the integrating spheres is lined with barium sulphate (BaSO4), which diffusely reflects around 98% of the light. The light is therefore optically integrated in the sphere via the reflective surfaces on the inside of the sphere, which allows the luminous flux to be measured in accordance with the requirements of CIE 127. For example, the small integrating sphere is where individual LEDs are measured or selected. The 250 mm integrating sphere allows the engineers to measure the semi spherical space (steradian: 2p) above a small circuit board, and hence an LED. This means that the personnel can for example select, in a 250 mm integrating sphere, LEDs with a precisely defined wavelength if five identical LEDs are needed. However, an appropriately sized 4p sphere is required for measuring an entire light. For this reason, EBV has also acquired an integrating sphere with an internal diameter of 1,000 mm (steradian: 4p) for “all-around measurements”, in addition to the 250 mm sphere. This large 4p integrating sphere is also ideal for comparative measurements – for example between filament or halogen bulbs and LED lamps – or for the CIE compliant measurement of high-power LEDs and entire lights with an edge length of up to 90 cm. A special holder inside the spheres allows an E27 fixture or light to be attached for this purpose. EBV also provides the right mechanical adapters for measurements in the sphere.
A core element of all the measuring technology in the EBV LightLab is the CAS 140CT spectroradiometer from Instrument Systems, which is designed to perform industry reference measurements under continuous 24-hour operation
This high-precision device measures the spectral power distribution of a 1,100 nm light source (infrared) within milliseconds through the visible light spectrum into the UV range at 380 nm – with a data point interval of 0.8 nm over a very high intensity measuring range of nine decades, which corresponds to a dynamic range of 1:1,000,000,000. All of the measured values are output via the USB bus to a PC/laptop/ notebook, where the SpecWinPRO software then handles further processing of the data in Windows (XP and higher). Not only does this software deliver the measurement data in the form of individual items of data in a table, it also displays the spectral distribution and position in the colour diagram in graphic form. In this way, the software also calculates the colour temperature and colour rendering index (CRI) on the basis of the measured values. Here, the device measures ‘only’ the radiometric output; to determine the photometric output, the software evaluates the radiometric spectral measurement data on the basis of the sensitivity curve of the human eye and outputs the luminous flux in lumens. Using a plug-in, the SpecWinPRO software controls a Keithley source meter. This means that the entire measurement process can be controlled via software – from the electrical activation of the LED to the details of the data output and data processing. The light to be measured reaches the analysis device via CIE compliant optical probes and a fibreoptic cable.
Type LEDGON 100 from Instrument Systems
With the aid of a goniophotometer, we are able to determine the angle-dependent directional characteristics of individual LEDs and smaller LED modules – and this with an angular resolution of 0.1° throughout the entire half-space in the beam direction of the LED. In combination with the spectroradiometer CAS 140CT already mentioned above, this will also enable EBV Elektronik to measure various spectral parameters such as colour co-ordinates or colour temperature as a function of angle. Since a number of different parameters of white LEDs – such as the colour temperature – vary significantly with the beam angle, these measurements play a very important role. While geometry-related measurement errors can occur in measurements performed in an integrating sphere, the goniophotometer – which is equipped with servo motors and controlled fully automatically by the SpecWinPRO software – is also ideal for precisely determining the radiant power and luminous flux and, in turn, the allimportant luminous efficiency quotient, which is specified in lm/W. The SpecWinPRO software is again used for the goniophotometer for processing and presenting the measurements, which are then available in the IES and EULUMDAT export formats for further processing. These data formats represent the characteristic beam data for an LED, and they can then be used as the starting data point for the simulation of a complete lamp
The 2440 Source Meter from Keithley
It is essentially a high-precision, programmable constant current and constant voltage source for actuating LEDs and LED modules under test conditions in the EBV LightLab. The current and voltage can be precisely set via the serial interface. To minimise the load on the light sources during the measurements, the source meter can be softwarecontrolled so that the LEDs are switched on only during the actual measurement but remain switched off during gaps between measurements. The 2440 source meter is also an ultra-high-precision volt and ampere meter that transfers the current, voltage and power data to the measurement software via an interface.
Luxmeter and light density
LightLab also features two lighting measurement devices, the Mavo-Spot 2 light density measuring device and the Mavolux 5032B luxmeter
By focusing on objects such as roads, tunnels, sports grounds or airfields from a distance, the Mavo-Spot 2 ‘light density camera’ enables corresponding light density measurements (unit: cd/m2) to be performed. It can also be used for determining the light density of displays, monitors or projection screens. The angle of detection of the Mavo- Spot 2 is just 1°, which allows for a highly precise selection of the measurement points or pixels on which the device focuses. The measurement object can be located anywhere from 34 cm to an infinite distance away from the device. The Mavolux light meter allows users to calculate the illumination levels (measured in lux) at the workplace and on other surfaces.
Customer will receive at the end, measurement reports containing all requested measurement data for their specific LED equipment
Beside of all mentioned measurement equipment there are various pieces of equipment, ranging from small tools through miniature drills to special stations for the temperature controlled soldering of LEDs onto MCPCBs, which ensure that users themselves can carry out small modifications or repairs directly in the EBV LightLab. LightLab also includes an infrared camera. This camera allows ‘hot spots’ on circuit boards to be identified in good time so that thermal management (i.e. the proper dissipation of thermal losses) can be optimised on the basis of this data.Beside that there are also a wide range of universal multimeters that measure not only the actual effective values of voltages and currents, but also the effective power values. These devices also enable the measurement of resistances, frequencies and capacitances. Also featured by the EBV LightLab is equipment for measuring and monitoring temperature.