Notes on the use of illuminance meters
①Photocells should be selenium (Se) photocells or silicon (Si) photocells with good linearity; they can still maintain good stability over a long period of time and have high sensitivity; when high E is used, the photocells with high internal resistance are used, which have low sensitivity and good linearity, and are not easy to be damaged by the strong light irradiation.
② V (λ) correction filters paid inside, suitable for illuminance with different color temperature light source, small error.
③ photocell before adding a cosine angle compensator (opal glass or white plastic) because the incident angle is large, the photocell deviates from the cosine rule.
④ illuminance meter should work at room temperature or near room temperature (photocell drift with temperature change and change).
Calibration of the illuminometer:
Principle of calibration:
Make Ls perpendicular irradiation photocell → E = I/r2, change r can be obtained under different illumination of the light current value, by the corresponding relationship between E and i will be converted to the current scale illuminance scale.
Calibration method:
The use of light intensity standard lamp, in close proximity to the working distance of the point light source, change the photocell and the standard lamp distance l, recorded under the distance of the ammeter readings, by the inverse square law of distance E = I / r2 calculation of light illuminance E, which can be obtained from a series of different illuminance of the light current value of i, for the photocurrent i and the illuminance of E curve, that is, for the illuminance of the calibration curve from this illuminance can be made to dial The calibration curve of the illuminometer can be divided into degrees, which is the calibration of the illuminometer.
Factors affecting the calibration curve:
Photocells and ammeter replacement needs to be re-calibrated; illuminance meter use for a period of time should be re-calibrated illuminance meter (generally within a year should be checked 1-2 times); high-precision illuminance meter can be used to check the light intensity of the standard lamp; expanding the range of calibration illuminance meter can change the distance r, you can also choose a different standard lamps, the choice of a small range of the ammeter.
