Tuesday, 9 April 2013

Measuring the illuminance and chromaticity of LEDs

The robust and reliable spectro-radiometer MK-350 was conceived by UPRtek as a cost-effective, mobile precision tool to measure, analyze and store the most important photometric parameters in the specification and qualification of LED, OLED and EL lamps and other luminaries. MK-350 is well suited for field use in the light design of studios and workplaces, as well as in research and development.

MK-350 is based on a high-resolution (1 nm) linear CMOS sensor (receptor diameter 6.6mm) and an advanced spectroscopic architecture with embedded processor. Its spectral half-bandwidth is specified to approx. 12 nm. The extremely compact (144 mm x 78 mm x 24 mm) and lightweight (250 g) instrument operates on rechargeable battery power. It performs an automatic dark calibration every time it is switched on.

The measurement results are instantly displayed in its 3.5-inch LCD color screen (320 x 240 pixels), which also serves as a convenient touch control interface. The instrument offers four basic operational modes: "Basic" indicates the numeric value of the measured illuminance between 70 and 70,000 lux, the correlated color temperature (CCT) in Kelvin, the standardized color rendering index (CRI) expressed as Ra value (average of the first eight test colors) and the peak wavelength of the light source's radiated spectrum in nm.

In the second measuring mode, "Spectrum", the MK-350 displays a detailed graph of the spectral energy distribution in the radiated wavelength bands (between 360 and 750 nm) according to the measurement distance. Integration time is adjusted automatically or manually between 8 and 1000 ms.

The other two MK-350 operational modes, "CIE1931" and "CIE1976", provide the CIE chromaticity coordinates x and y, resp. u' and v', within their standardized CIE color space diagrams. Together with the measured illuminance, this enables an evaluation of LEDs in terms of their perceptional color performance for sorting and binning tasks during manufacturing or in the field.

MK-350 measures illuminance at an accuracy of +5%. Color temperature is determined within +2%. Color accuracy (according to CIE1931) is +0,0025, at a repeatability of +0,0005, both measured at 20,000 lux and 2856 K. CRI accuracy expressed as Ra is determined within +1,5%.

Measurement is initiated by touch control, either as one-time or continuous capture at selectable intervals. All measurement data (up to 2,000 files) are stored on an optional 2 GB SD-Card in an Excel- or bmp-compatible format. An USB2.0 port enables easy data transfer. The built-in Li-Ion battery (3.7 V/ 2.5 Ah) ensures 5 hours of operation time. Operating temperature is 0 to 35 °C. Menu languages are Chinese (traditional and simplified) or English, with a German version downloadable shortly.

• Distributor for Central Europe is Saleslink GmbH in Udenheim (D).

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