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LED Testing | Measurement of LED Tests

This article on LED testing covers various test and measurement parameters used for LED tests. It mentions test setup used for various measurements during LED testing.

What is LED?

Introduction: • LED stands for Light Emitting Diode.
• It is made using gallium arsenide phosphide compound.
• It radiates infrared light at wavelength of 850 nm.
• It has two leads viz. long (called "anode") and short (called "cathode"). Anode terminal is positive and cathode terminal is negative.
• LEDs are used in various devices as indicators. It is used in various electronic devices, circuit boards for debugging purpose.
• The figure-1 depicts LED appearance and LED symbol.

LED appearance and symbol

• LED types are caterized as in-organic LEDs and organic LEDs. Inorganic LEDs are made using inorganic materials such as AlGaAs, GaAsP etc. Organic LEDs (OLEDs) are made using organic materials i.e. very thin film of such material is printed on substrate made using glass material. QLEDs (Quantum dot LEDs) have been developed recently.
• It is used in fiber optic and other light based communication systems for lower speed (30 Mbps).
• They are very cheap source of lights which consume very less power.

Measurements of LED Tests

Typical parameters of the LEDs are as follows.
• Sizes: 3, 5, 8 or 10 mm.
• Colors: white, blue, green, orange, yellow, multi-color
• Voltage: 1.8 to 2.2 V (LED number RR991-04), current: 20 mA
• Intensity (in mcd), colour frequency and viewing angle are other parameters.
• Life span
• Quantum efficiency
• Power output
• Quantum-Efficiency

LED testing youtube video

There numerous videos available on Youtube for testing LED. The below video shows testing the LED using digital multimeter.

Test Setup for LED Testing

Following figure-2 depicts test setup used for verification of LED during LED testing. Setup is simple and requires multimeter only.

LED testing setup

➤Keep the multimeter in "diode" test first.
➤Forward bias test: Connect the "RED" cable with positive terminal and "BLACK" cable with negative terminal. In this connection LED will glow and voltage is about 1.8 V in the multimeter display.
➤Reverse bias test: Connect the "RED" cable with negative terminal and "BLACK" cable with positive terminal. In this connection, current flow is blocked and hence LED will not glow.



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