Apogee MQ-501 Owner's Manual - Page 11

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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 Error

The combination of diffuser transmittance, interference filter transmittance, and photodetector sensitivity yields

spectral response of a quantum sensor. A perfect photodetector/filter/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 SQ-100

and SQ-500 series quantum sensors using the method of Federer and Tanner (1966). This method requires PPFD

weighting factors (defined plant photosynthetic response), measured sensor spectral response (shown in Spectral

Response section on page 7), and radiation source spectral outputs (measured with a spectroradiometer). Note,

this method calculates spectral error only and does not consider calibration, cosine, and temperature errors.

Spectral error data (listed in table below) 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), but larger errors for different mixtures

of light emitting diodes (LEDs) for the SQ-100 series. Spectral errors for the SQ-500 series sensors are smaller than

those for SQ-100 series sensors because the SQ-500 spectral response is a closer match to the defined plant

photosynthetic response.