Apogee SQ-225 Instrukcja obsługi - Strona 13
Przeglądaj online lub pobierz pdf Instrukcja obsługi dla Akcesoria Apogee SQ-225. Apogee SQ-225 16 stron. Quantum sensor
Spectral Errors and Yield Photon Flux Measurements
Apogee quantum sensors are calibrated to measure PPFD for either sunlight or electric light. The difference between the
calibrations is 12 %. A sensor calibrated for electric lights (calibration source is T5 cool white fluorescent lamps) will read
approximately 12 % low in sunlight.
In addition to PPFD measurements, Apogee SQ series quantum sensors can also be used to measure yield photon flux
density (YPFD): photon flux weighted according to plant photosynthetic efficiency (McCree, 1972) and summed. YPFD is also
expressed in units of µmol m
PPFD is usually measured and reported because the PPFD spectral weighting function (equal weight given to all photons
between 400 and 700 nm; no weight given to photons outside this range) is easier to define and measure, and as a result,
PPFD is widely accepted. The calibration factor for YPFD is 0.9 µmol m
µmol m
-2
s
-1
per mV for models SQ-215 and SQ-225.
The weighting functions for PPFD and YPFD are shown in the graph below, along with the spectral response of Apogee SQ
series quantum sensors. The closer the spectral response matches the defined PPFD or YPFD spectral weighting functions,
the smaller spectral errors will be. The table below provides spectral error estimates for PPFD and YPFD measurements from
light sources different than the calibration source. The method of Federer and Tanner (1966) was used to determine spectral
errors based on the PPFD and YPFD spectral weighting functions, measured sensor spectral response, and radiation source
spectral outputs (measured with a spectroradiometer). This method calculates spectral error and does not consider
calibration, cosine, and temperature errors.
Federer, C. A., and C. B. Tanner, 1966. Sensors for measuring light available for photosynthesis. Ecology 47:654-657.
McCree, K. J., 1972. The action spectrum, absorptance and quantum yield of photosynthesis in crop plants. Agricultural
Meteorology 9:191-216.
s
, and is similar to PPFD, but is typically more closely correlated to photosynthesis than PPFD.
-2
-1
s
per mV for models SQ-212 and SQ-222, or 0.45
-2
-1
Radiation weighting factors for PPFD
(defined plant response to radiation),
YPFD (measured plant response to
radiation), and Apogee SQ Series
quantum sensors (sensor sensitivity to
different wavelengths of radiation).
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