Structural principle of the illuminance meter: The illuminance meter consists of two parts: a photometric head (also called a light-receiving probe, including a receiver, a V (λ) pair filter, and a cosine corrector) and a reading display. Selenium (Se) photovoltaic cells or silicon (Si) photovoltaic cells are commonly used as illuminance meters, also known as lux meters.

1. Photovoltaic cells should use selenium (Se) photovoltaic cells or silicon (Si) photovoltaic cells with good linearity; they can maintain good stability for a long time and have high sensitivity; when the E is high, use photovoltaic cells with high internal resistance, which have low sensitivity and linearity. Good, not easily damaged by strong light;

2. There is a V (λ) correction filter inside, which is suitable for illumination of light sources with different color temperatures and has small error;

3. Add a cosine angle compensator (opalescent glass or white plastic) in front of the photovoltaic cell because when the incident angle is large, the photovoltaic cell deviates from the cosine law;

4. The illuminance meter should work at room temperature or close to room temperature (photocell drift changes with temperature changes).

1. Visual illuminance meter: inconvenient to use, not very accurate, and rarely used;

2. Photoelectric illuminance meter: Selenium photovoltaic illuminance meter and silicon photovoltaic illuminance meter are commonly used.