2023 EDM




Source Measure Unit Application - LED Test and Measurement




LED is the abbreviation of Light Emitting Diode, which is widely used in lighting, LCD display backlight, mobile phones, information display, status indicators, and other applications, including information transmission (such as IrDA infrared transmission, Li-Fi optical communications technology Light Fidelity), signal conversion (such as infrared thermal imaging, optocoupler), and more applications in biomedical applications, such as UV sterilization.


The characteristics tests of LEDs, the same as that of conventional light sources, need to determine LED characteristics through standard measurement methods, such as measuring luminous flux, luminous intensity, luminance, illuminance, etc. These tests must follow the regulations formulated by the International Commission on Illumination (CIE).  Standards formulated afterwards such as CIE1931 and CIE1976 became the foundation of colorimetry.





LED Test System Using GW Instek GSM-20H10



When testing the characteristics of LEDs, equipment such as spectrometers, integrating spheres, and source measure units are required. The connection method involves using a computer to control the output of the power source (such as a source measure unit) and the light source receiving measurement end (such as a spectrometer) to control and measure the LED.



Connection method of LED test



To test an LED using a source measure unit, the following steps should be followed:


  1. Set the output voltage and current of the source measure unit according to the LED's rated voltage and current. Typically, the operating current of an LED is in the range of μA to mA, while the rated voltage is within 20V.
  2. Connect the positive and negative terminals of the source measure unit to the positive and negative terminals of the LED, and set the corresponding current and voltage.
  3. Set the desired power supply mode, either constant current (CC) or constant voltage (CV) mode.
  4. Set the output parameters of the source, such as current, voltage, and measurement time.
  5. Start the output of the source and begin the measurement.
  6. Determine the characteristics of the LED, such as forward current and operating voltage, based on the reading of the meter.


A complete LED test not only includes data such as spectral graph, illuminance, and color temperature, but also records the parameters and values of each measurement. As shown in the figure below, the test in this article was conducted in accordance with the color quality TM30 regulations for LED testing. In addition to the parameters required for the LED, the voltage changes under CC mode were also recorded one by one in the parameter settings, allowing engineers to perform more characteristic analysis.



LED Testing for Color Quality TM30 Regulations



For more detailed application content, please go to www.gwinstek.com/en-global/products/detail/GSM-20H10



Please contact us for further information of GSM-2010.


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