Apogee MQ-100 Manuale d'uso - Pagina 11

Sfoglia online o scarica il pdf Manuale d'uso per Strumenti di misura Apogee MQ-100. Apogee MQ-100 18. Quantum meter

overwrite the oldest measurement once there are 99 measurements. Every 48 averaged measurements (making a 24 hour

period), the meter will also store an integrated daily total in moles per meter squared per day (mol m

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Reset: To reset the meter, in either SMPL or LOG mode, push the mode button three times (RUN should be blinking), then

while pressing the down button, press the mode button once. This will erase all of the saved measurements in memory, but

only for the selected mode. That is, performing a reset when in SMPL mode will only erase the manual measurements and

performing a reset when in LOG mode will only erase the automatic measurements.

Review/Download Data: Each of the logged measurements in either SMPL or LOG mode can be reviewed on the LCD

display by pressing the up/down buttons. To exit and return to the real-time readings, press the sample button. Note that the

integrated daily total values are not accessible through the LCD and can only be viewed by downloading to a computer.

Downloading the stored measurements will require the AC-100 communication cable and software (sold separately). The

meter outputs data using the UART protocol and requires the AC-100 to convert from UART to USB, so standard USB cables

will not work. Set up instructions and software can be downloaded from the Apogee website

(http://www.apogeeinstruments.com/ac-100-communcation-cable/).

Spectral Errors and Yield Photon Flux Measurements

Apogee quantum meters are calibrated to measure PPFD for either sunlight or electric light (menu selectable). 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 MQ series quantum meters can also be used to measure yield photon flux

density (YPF): photon flux weighted according to the plant photosynthetic action spectrum (McCree, 1972) and summed.

YPFD is also expressed in units of µmol m

, and is similar to PPFD, but is typically more closely correlated to

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photosynthesis than PPFD. 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 conversion factor to calculate YPFD from the PPFD measurements

displayed on the LCD is 0.90 and 0.89 for sunlight and electric light measurements, respectively.

The weighting functions for PPFD and YPFD are shown in the graph below, along with the spectral response of Apogee

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.