help info

1

For best accuracy, ensure comparison is made on a clear, non-polluted, summer day within one hour of solar noon.

2

Select the sensor for comparison by using the buttons at the top of the page.

3

Enter the postal code, date, and time and click Calculate Model to autofill the remaining parameters.

4

For a more accurate estimation, deselect Autofill Parameters and manually enter the remaining input parameters. Hover over the input field or click the help icon at the top of the page for an explanation of input parameters.

5

Enter your measurement result from your sensor in the Measured PPFD cell. The sensor must be level and perfectly clean for an accurate reading.

6

If the difference from the model estimated value is outside the selected sensor's threshold, the text will turn red and a button will appear to contact Apogee for recalibration.

Model Estimated PPFD

=

µmol m-2 s-1

Measured PPFD

=

µmol m-2 s-1

Difference from Model

=

%

Contact Apogee for Recalibration

Postal Code

=

Country

=

Date

=

Time

=

Autofill Parameters

Daylight Savings

=

Timezone

=

Latitude

=

°

Longitude

=

°

Elevation

=

Air Temperature

=

Relative Humidity

=

%

Calculate Model
Calculation Updated

Calculated Intermediate Variables

Solar Constant

=

W m-2

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Solar constant for the mean distance between the Earth and Sun

Energy in PAR

=

J mol-1

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Average energy content of photosynthetically active radiation (PAR)

PAR / Solar

=

J mol-1

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Ratio of photosynthetically active radiation (PAR) to incoming shortwave radiation (SWi)

UV-A / Solar

=

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Ratio of Ultraviolet A (UV-A) to incoming shortwave radiation (SWi)

Longitudetz

=

°

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Longitude of the center of your local time zone, expressed as positive degrees west of the standard meridian in Greenwich, England

Kt

=

1.0

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Atmospheric turbidity coefficient (must be set to 1 for clean air)

dr

=

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Inverse relative distance factor for the distance between Earth and sun

δ

=

°

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Solar declination

eqt

=

min

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Equation of time (More info on NOAA Website)

Solar N

=

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Time of solar noon

Solar Z

=

°

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Solar zenith angle

PB

=

kPa

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Barometric pressure of the measurement site

eA

=

kPa

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Air vapor pressure

w

=

mm

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Precipitable water in the atmosphere

Kb

=

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Clearness index for direct beam radiation

Kd

=

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Transmissivity index for diffuse radiation

SWa

=

W m-

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Extraterrestial radiation

SWi

=

W m-2

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Shortwave Irradiance