Measuring principle and requirements of illuminance meter
1. Measuring principle
A photovoltaic cell is a photoelectric element that directly converts light energy into electrical energy. When the light hits the surface of the selenium photovoltaic cell, the incident light passes through the metal thin film 4 and reaches the interface between the semiconductor selenium layer 2 and the metal thin film 4, generating a photoelectric effect on the interface. The magnitude of the generated photocurrent has a certain proportional relationship with the illuminance on the light-receiving surface of the photocell. At this time, if an external circuit is connected, a current will flow, and the current value will be indicated on the microammeter with lux (Lx) as the scale. The magnitude of the photocurrent depends on the intensity of the incident light. The illuminance meter has a shifting device, so it can measure high illuminance or low illuminance.
2. Requirements for use:
The probe of the illuminance meter is made of glass, which is easy to be broken and damaged. At the same time, the waterproof effect is very poor when used.
① Photocells should use selenium (Se) photocells or silicon (Si) photocells with good linearity; they can still maintain good stability and high sensitivity after working for a long time; when E is high, choose photocells with high internal resistance, which have low sensitivity and good linearity , not easily damaged by strong light
② There is a V(λ) correction filter inside, which is suitable for the illumination of light sources with different color temperatures, and the error is small
③Add a cosine angle compensator (opalescent glass or white plastic) in front of the photocell because when the incident angle is large, the photocell deviates from the cosine rule
④The illuminance meter should work at room temperature or close to room temperature (photocell drift changes with temperature change)
