The disadvantage of the high-resolution formats is that it takes more memory per data point.
7.6 Spectral error
The combination of diffuser transmittance, interference filter transmittance, and photodetector
sensitivity yields spectral response of a quantum sensor. A perfect photodetector, filter, and
diffuser combination would exactly reproduce the defined plant photosynthetic response to
photons (equal weighting to all photons between 400 and 700 nm), but this is challenging in
practice. Mismatch between the defined plant photosynthetic response and sensor spectral
response results in spectral error when the sensor is used to measure radiation from sources with
a different spectrum than the radiation source used to calibrate the sensor (Federer and Tanner,
1966; Ross and Sulev, 2000).
Spectral errors for PPFD measurements made under different radiation sources were calculated
for the CS310 quantum sensor using the method of Federer and Tanner (1966). This method
requires PPFD weighting factors (defined plant photosynthetic response), measured sensor
spectral response (
(p. 5)), and radiation source spectral outputs (measured with a
spectroradiometer). This method calculates spectral error only and does not consider calibration,
cosine, and temperature errors. Spectral error data (TABLE 8 1) indicate errors typically less than
5% for sunlight in different conditions (clear, cloudy, reflected from plant canopies, transmitted
below plant canopies) and common broad spectrum electric lamps (cool white fluorescent, metal
halide, high pressure sodium).
Table 7-3: Spectral errors for PPFD and YPFD measurements
Radiation source (error calculated
relative to sun, clear sky)
PPFD error [%]
Sun (clear sky)
0.0
Sun (cloudy sky)
0.5
Reflected from grass canopy
0.0
Transmitted below wheat canopy
1.1
Cool white fluorescent (T5)
2.2
Metal halide
3.1
Ceramic halide
1.9
High pressure sodium
2.2
Blue LED
(448 nm peak, 20 nm full-width half-maximum)
3.0
CS310 Quantum Sensor
11
