Lighting Retrofits: Putting Technology to Work

Part 1: Lighting Controls: A Look at Daylight Harvesting

Part 2: Photosensors: What Are Typical Light-Level Ranges?

Part 3: Daylight Harvesting: The Importance of Signal Resolution

Part 4: Daylight Harvesting: What is Photopic Correction?

Part 5: Photosensors: Wireless, Self-Calibrating Products Emerge

Photosensors: What Are Typical Light-Level Ranges?

By Craig DiLouie - February 2010

Photosensors might be limited in the range of light levels they can detect. They perform dusk and dawn lighting control at fewer than 10 footcandles (fc), they control daylit offices at less than 100 fc, and they control atrium spaces at fewer than 1,000 fc. Skylight sensors see up to 10,000 fc of sunlight.

Below are several typical light-level ranges photosensors detect for specific applications:

1-500 fc for a photosensor mounted on a ceiling in a space with a window
10-5,000 fc for a photosensor mounted in an atrium or skylight
100-10,000 fc for a photosensor mounted outside a building.

"Lighting designers should ensure that the range of response of the photosensor matches the light levels likely to be found in the area of installation," says Solayappan Alagappan, design engineer with Philips.

Photosensors: What To Ask

Managers can ensure success when specifying photosensor technology by getting answers to essential questions:

Is it compatible with the given controller?
What control method does the system use?
What is the sensor's spatial response?
What range of light levels can it detect?
How accurate is its signal?
Is it corrected for photopics?
How far is the installation site from its controller?
How will technicians commission it?
How many zones can it support?
What are the configuration options?
Can it operate reliably within the given environment — heat, cold, moisture, etc.?
Do listing or compliance requirements, such as Underwriters Laboratories (UL) or restriction of hazardous substances (ROHS), come into play?