LED lighting installation needs to be tested
1. Luminous intensity detection: Due to the concentration of light from the LED, the inverse square law is not suitable for short distances. The CIE217 standard provides two conditions for measuring the average normal light intensity, measurement condition A (far-field condition) and measurement condition B (near-field condition). The detector area in both cases is 1 square centimeter. Generally, light emission condition B is used to detect light emission intensity.
2. Detection of luminous flux and efficiency: The detection methods mainly include the following 2 types. (1) Integral method, the standard lamp and the tested lamp are lit sequentially in the integrating sphere, and their readings in the photoelectric converter are counted as Es and Ed. If the standard luminous flux is called Φs, the measured luminous flux Φd=ed×Φs /es. The integration method adopts the principle of "point light source", and the operation is simple, but due to the color temperature deviation between the standard lamp and the detected lamp, the measurement error is large. (2) Spectrophotometry. The luminous flux is calculated from the spectral energy P(λ) distribution. Using a monochromator, measure the 380nm~780nm spectrum of the standard lamp on the integrating sphere, then measure the spectrum of the lamp under the same conditions, and measure the luminous flux of the lamp by comparison. Luminous efficiency is the ratio of the luminous flux emitted by the light source to the power consumed. The constant current method is usually used to measure the luminous efficiency of light-emitting diodes.
3.Detection of spectral characteristics:The detection of the spectral characteristics of light-emitting diodes includes spectral power distribution, color coordinates, color temperature, color rendering index, etc. Spectral power distribution means that the light of the light source is composed of many colored radiations of different wavelengths, and the radiation power of each wavelength is also different. When the light sources are arranged in order of wavelength, this difference is called the spectral power distribution of the light source. Compare and measure the light source with a spectrophotometer (monochromator) and a standard lamp. The color coordinate is the amount of the light emission color of the light source represented by a number on the graph. There are many coordinate systems for color charts. X and Y coordinate systems are usually used. The color temperature is the number of light source color tables (appearance color representation) seen by the human eye. When the light emitted by the light source is the same color as the light emitted by the black body at a certain temperature, the temperature is the color temperature. In the field of lighting, color temperature is an important parameter that describes the optical characteristics of a light source. The relevant theory of color temperature is derived from black body radiation, and can be obtained from the color coordinates including the blackbody locus by the color coordinates of the light source. The color rendering index indicates the amount of light emitted by the light source that correctly reflects the color of the illuminated object. It is usually represented by the general color rendering index Ra, which is the arithmetic average of the color rendering indexes of the light sources of eight color samples. The color rendering index is an important parameter of the quality of the light source, which determines the application range of the light source. Improving the color rendering index of white light-emitting diodes is one of the important tasks of light-emitting diode research and development.
4.The effect of temperature on the optical performance of light-emitting diodes: Temperature affects the optical characteristics of light-emitting diodes. A large number of experiments have shown that temperature affects the emission spectrum and color coordinates of light-emitting diodes.
5.Measurement of electrical parameters of LED lamps:The electrical parameters mainly include forward voltage, reverse voltage and reverse current, which are related to the normal operation of the LED lamp and are one of the basis for judging the basic performance of the LED lamp. There are two types of electrical parameter measurement for LED lamps: voltage parameters at a certain current; when the voltage is constant, the current parameters are tested. The specific methods are as follows: (1) DC voltage. When a forward current is applied to the LED lamp to be detected, a voltage drop will appear across the LED lamp. Adjust the power supply determined by the current value, and record the relevant reading on a DC voltmeter, which is the DC voltage of the LED lamp. According to related common sense, when the light-emitting diode is turned on forward, the resistance is smaller, and the external connection method of the ammeter is more accurate. (2) Reverse current. Apply reverse voltage to the tested LED lamp and adjust the regulated power supply. The ammeter reading is the reverse current of the LED lamp under test. Similar to DC voltage measurement, because the resistance of the light-emitting diode is relatively large during reverse conduction, the internal connection of the ammeter is used.
