Sensor type
Illuminance sensors are usually divided into two categories: photodiodes and photomultiplier tubes. Photodiodes are based on semiconductor materials that produce an electrical signal proportional to the intensity of light when illuminated. It has a fast response speed and a relatively simple structure, making it suitable for conventional visible light measurements. The photomultiplier tube realizes signal amplification through photoelectric effect and secondary electron multiplication, and has extremely high sensitivity, making it suitable for low-light environments. The spectral characteristics and intensity level of the measurement environment should be considered when choosing.
Measurement range considerations
The selection of the measurement range should be combined with the expected illuminance value of the application scenario. Everyday indoor lighting typically ranges from 100 to 1,000 lux, while outdoor cloudy days can reach thousands of lux and tens of thousands of lux in clear daylight. Sensor linearity and noise level affect the accuracy of range boundaries. It is recommended to select a range slightly higher than the actual maximum expected value and ensure sufficient resolution in low-light areas. The formula E=Φ/A can assist in estimation, where E is the illuminance, Φ is the luminous flux, and A is the illuminated area.
Environmental adaptability
The stability of the sensor to temperature, humidity, and angular response is a key factor. Some sensors may drift when the temperature fluctuates, and its temperature compensation mechanism needs to be investigated. The cosine correction function ensures accurate measurements of oblique incident light in line with cosine law correction. In a changing environment, choose a model with the appropriate package protection level and a viewing angle that matches the application requirements.
Calibration & Standards
Regular calibration is the basis for reliable measurements. Reference standards such as GB/T 5700 or CIE S 023 specify the performance requirements and calibration methods for illuminance meters. Sensors can decay over time, and it is recommended to perform laboratory calibration at standard cycles and check for spectral matching errors and nonlinear errors.
Selection suggestions
For comprehensive evaluation, the following control relationships can be referenced:
| Application scenarios | Sensor type tendencies |
| Interior lighting assessment | Photodiode |
| Low-light monitoring | Photoelectric multiplier tube |
| Wide dynamic range outdoors | Dual sensor or auto-ranging |
| Spectral studies | Spectral matching sensor |
The final selection should be based on actual measurement needs, environmental conditions, and long-term stability requirements, and validate compliance with relevant standards.
References
1. For the sensor type, refer to the description of the characteristics of photoelectric conversion devices in "Photoelectric Detection Technology".
2. The measurement range is partly based on the illuminance grading data of the Illuminating Engineering Society standard.
3. The calibration standard section refers to the National Lighting Measurement Code and CIE publications.