1. Photocells should use selenium (Se) photocells or silicon (Si) photocells with good linearity; Maintains good stability and high sensitivity even after prolonged work; When using high E, choose photocells with high internal resistance, which have low sensitivity and good linearity, and are not easily damaged by strong light irradiation;

2. Internal payment with V（ λ） Correct the filter, suitable for using the illumination of a heterochromatic temperature light source, with small errors;

3. The reason for adding a cosine angle compensator (milky white glass or white plastic) in front of the photocell is that when the incident angle is large, the photocell deviates from the cosine rule;

4. The illuminometer should operate at or near room temperature (the drift of the photocell changes with temperature).

1. Visual illuminometer: inconvenient to use, low accuracy, rarely used;

2. Photoelectric illuminometer: commonly used selenium photocell illuminometer and silicon photocell illuminometer.