Spectral Errors for PPFD Measurements with Apogee SQ-100X Series Quantum Sensors
Radiation Source (Error Calculated Relative to Sun, Clear Sky)
PPFD Error [%]
Sun (Clear Sky)
0.0
Sun (Cloudy Sky)
0.2
Reflected from Grass Canopy
5.0
Reflected from Deciduous Canopy
7.0
Reflected from Conifer Canopy
7.3
Transmitted below Grass Canopy
8.3
Transmitted below Deciduous Canopy
8.4
Transmitted below Conifer Canopy
10.1
Cool White Fluorescent (T5)
7.2
Cool White Fluorescent (T12)
8.3
Metal Halide
6.9
Ceramic Metal Halide
-0.9
High Pressure Sodium
3.2
Blue LED (448 nm peak, 20 nm full-width half-maximum)
14.5
Green LED (524 nm peak, 30 nm full-width half-maximum)
29.6
Red LED (635 nm peak, 20 nm full-width half-maximum)
-30.9
Red, Blue LED Mixture (80 % Red, 20 % Blue)
-21.2
Red, Green, Blue LED Mixture (70 % Red, 15 % Green, 15 % Blue)
-16.4
Cool White Fluorescent LED
7.3
Neutral White Fluorescent LED
1.1
Warm White Fluorescent LED
-7.8
Quantum sensors can be a very practical means of measuring PPFD from multiple radiation sources, but spectral
errors must be considered. The spectral errors in the table above can be used as correction factors for individual
radiation sources.
