How the integrated photometer works:
The light emitted by the luminaire is irradiated on the inner wall of the integrating sphere, and the surface of the inner wall coated with the diffuse reflection material is repeatedly reflected to form a uniform illuminance light, and then enters the spectroradiometer to form test data.
Therefore, there may be several reasons for testing the test data when using the integrating sphere to test the luminous flux:
There is a deviation between the standard lamp and the light distribution of the measured source. The larger the angle, the larger the deviation.
The standard lamp is different from the size of the lamp under test.
The adsorption of the appearance color of the tested lamp will reduce the reflected light flux and cause deviation.
The reflectivity of the inner wall of the integrating sphere decreases after a long time of use.
For the above four reasons, the luminous flux is sometimes 20% lower than the actual luminous flux when testing black small-angle spotlights, making the integrating sphere lose its meaning when testing the luminous flux.
The integrating sphere is calibrated with a standard lamp during the test. If the ideal data cannot be achieved after calibration or if the calibration data is more accurate, there is a correction factor inside the software, as shown in the figure below.
Test main page
Correction factor page
According to this principle, as long as the exact luminous flux of a lamp is known, the integrating sphere is the test data X when the correction coefficient is 1, and a coefficient is obtained by using the known accurate luminous flux /X, which is the correction coefficient. It is inconvenient to enter the correction factor page on the above figure. The correction factor can be input from the absorption position in the figure below. The result is the same.
The calculated correction factor is input and retested. The test result is the same as the determined luminous flux, and the error is within 2%. The calculated correction factor tests the lamp accurately, and tests whether other lamps are accurate. After nearly half a year of verification, the same type of lamp (downlight/spotlight, etc.) and structural size deviation are not large (such as 3W/6W/9W, etc.) A coefficient can be used.
This coefficient is saved. After the same type, the lamp with a small deviation in size can use the determined coefficient. The lamps tested by this method have excluded the traditional influence of the integral sphere, such as angle and color, mainly related to the shape and size of the lamp.
Lamps with known luminous flux can be tested with a distributed photometer. Different types and sizes of lamp distribution photometers can be determined only once, and the coefficients can be determined. After the same type, the same size lamps can be tested with only the integrating sphere. There is no need to distribute the photometer test, which greatly improves the test efficiency, so that the distribution photometer only measures the light with the light distribution requirement or the structure design is measured once in the light distribution design, and the subsequent test uses the integrating sphere.
At present, the new GB/T T33721 luminaire reliability test needs to be tested once at the initial time, once after the reliability test, and once after the life test, if the optical fading device is still unable to meet the test requirements by the distributed photometer. If you use the improved method to test, you can fully meet the test requirements, and the distribution of the photometer will not need to be queued for a long time, and you don't have to worry about the equipment problem affecting the test progress. The new method can increase test efficiency by 3-4 times.
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