The SQ-640 Light Pollution Sensor from Apogee Instruments can detect trace amounts of light from 340 to 1040 nm. The graph below shows data collected in a windowless room in the Apogee building using an
SQ-640 Light Pollution Sensor and an
AT-100 µCache Bluetooth datalogger. The light pollution sensor was placed in the back of the room about 25 feet (8 m) from the door. To calibrate the sensor dark offset value, a dark scan was performed with the sensor covered. Photodetectors have small dark signals that need to be determined and removed from measured data in order to maximize accuracy. The µCache automatically adjusts for the dark offset once the dark scan has been performed. Data were then collected while the door was progressively closed, limiting incoming light from the adjoining hallway. With 20-point smoothing, the µCache logger and SQ-640-SS sensor were able to resolve light measurements as fine as 0.002 micromoles m
-2 s
-1, or 2 nanomoles m
-2 s
-1.
