Follow

SSI Photocells: What Are The Photocell "Thresholds"?

Each photocell will have a set number of foot candles it will try to keep its foot candle measurement above.  The specific threshold a given product will maintain is a result of the combination of the Set Point and the Sunlight Discount Factor.  Keep in mind that the light level will be maintained at the sensor and not necessarily at the work surface.

When active, On/Off Daylighting Control products will be comparing their foot candle measurement to one of two thresholds.  If the light the sensor is controlling is off, then the sensor will compare its foot candle measurement to its Set Point multiplied by its Sunlight Discount Factor.  If the foot candle measurement ever goes beneath this threshold the sensor will start its countdown to turn the lights on.

If the light the sensor is controlling is on, then the sensor will compare its foot candle measurement to its Set Point multiplied by its Sunlight Discount Factor plus the measured artificial contribution of the lights it is controlling and a safety factor.  If the foot candle measurement ever goes above this threshold the sensor will start its countdown to turn the lights off.  The measured artificial contribution of the lights it is controlling must be included to ensure when the lights are switched off that the underlying threshold is maintained.  Otherwise the lights could cycle on and off going above and below the threshold forever.  The measured artificial contribution of the lights and the safety factor are sometimes referred to as the Deadband.

Was this article helpful?
0 out of 0 found this helpful
Have more questions? Submit a request

Comments

Powered by Zendesk