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
Apogee SQ-100X series sensors can measure PPFD for sunlight and electric light with a single calibration factor.
However, errors occur in various light sources due to changes in spectral output. If the light source spectrum is
known then errors can be estimated and used to adjust the measurements. The weighting function for PPFD is
shown in the graph below, along with the spectral response of Apogee SQ-100X series quantum sensors. The closer
the spectral response matches the defined PPFD spectral weighting functions, the smaller spectral errors will be.
The table below provides spectral error estimates for PPFD 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 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.