Testing the Light Distribution of Street and Area Lighting
The distribution of light from street and area lighting fixtures is a critical aspect of outdoor lighting design. Properly designed lighting can improve safety, security, and visibility while reducing energy consumption and environmental impact. However, poorly designed lighting can create glare, discomfort, and unnecessary energy consumption.
Lighting designers and engineers use various methods to test the light distribution of street and area lighting fixtures. These tests involve measuring the lumens per square meter (lm/m²) at different points around a fixture, typically using a photometer or lux meter. The results are then compared to the manufacturers specifications and design intent.
Understanding Light Distribution
There are several key factors that affect light distribution, including:
Beam Angle: This refers to the angle between the center of the beam and the edge of the beam. A narrower beam angle (e.g., 10) produces a more focused beam with higher intensity at the center but lower intensity towards the edges. A wider beam angle (e.g., 30) produces a broader, more even illumination.
Lumen Output: This measures the total amount of light emitted by a fixture in all directions. Higher lumen output fixtures produce brighter areas and are often used for high-traffic or security lighting applications.
Testing Light Distribution
To test the light distribution of street and area lighting fixtures, follow these steps:
1. Choose a Test Location: Select a location with a flat surface, such as a parking lot or field.
2. Set Up Measuring Equipment: Position a photometer or lux meter at different distances from the fixture to measure the lumens per square meter (lm/m²).
3. Take Multiple Measurements: Record measurements at multiple points around the fixture to capture both high and low areas.
4. Compare Results to Manufacturer Specifications: Compare the test results to the manufacturers specifications for beam angle, lumen output, and light distribution patterns.
Example of a Light Distribution Test
Consider a street lighting fixture with a 30 beam angle and 20,000 lumens per hour (lm/h). The following measurements are taken at different distances from the fixture:
Distance Lumens Per Square Meter (lm/m²)
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5 meters 1.2 lm/m²
10 meters 0.6 lm/m²
15 meters 0.3 lm/m²
Light Distribution Patterns
Street and area lighting fixtures are designed to produce specific light distribution patterns, including:
Circular: Uniform illumination in all directions.
Elliptical: Concentrated illumination along the fixtures long axis.
Linear: Illumination along a single axis.
When testing light distribution, it is essential to understand these patterns and how they align with the design intent.
QA
What are the common mistakes when testing light distribution?
A: Common mistakes include failing to account for atmospheric conditions (e.g., fog, dust), not using calibrated measuring equipment, or neglecting to consider the fixtures age and maintenance history.
How often should light distribution tests be performed?
A: Regular testing is recommended every 2-5 years, depending on the lighting systems design life and maintenance schedule. Factors like climate, pollution, and fixture aging can affect performance over time.
What are the benefits of accurate light distribution testing?
A: Accurate light distribution testing ensures that fixtures operate as intended, improving safety, security, and visibility while reducing energy consumption and environmental impact.
Can I use a smartphone app to measure light distribution?
A: While smartphone apps can be useful for basic measurements, they may not provide the accuracy required for professional lighting design. Consider investing in a photometer or lux meter specifically designed for this purpose.
How do I choose the correct measuring equipment for my test?
A: Select equipment that meets industry standards (e.g., IES LM-49) and is calibrated regularly to ensure accurate measurements.
What are some common light distribution patterns used in street lighting?
A: Common patterns include circular, elliptical, and linear distributions. The choice of pattern depends on the application, available space, and design intent.
Can I adjust a fixtures orientation to improve its light distribution?
A: Yes, adjusting the fixtures orientation can significantly impact its performance. However, consider factors like glare control, sightline obstruction, and maintenance access when making adjustments.
By following these guidelines and staying informed about lighting standards and technologies, you can ensure that your outdoor lighting system operates efficiently and effectively, meeting the needs of both users and the environment.
