Apogee SU-100 Owner's Manual - Page 10
Browse online or download pdf Owner's Manual for Accessories Apogee SU-100. Apogee SU-100 16 pages. Ultraviolet sensor
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Sensor Calibration
The SU-100 has a standard UV calibration factor of exactly:
Multiply this calibration factor by the measured mV signal to convert sensor output to UV in units of µmol m
Calibration Factor (5.0 µmol m
5.0
Full Sunlight
175 µmol m
-2
UV-B Measurements and Spectral Errors
Apogee Instruments model SU-100 UV Sensors measure ultraviolet radiation between 250 and 400 nm in micromoles of
photons per square meter per second. Although the UV radiation between 280 and 315 nm (UV-B) is critically important in
photochemical and photobiological reactions, less than 3 % of the UV photons are in this range. Because only a small fraction
of the photons are in the UV-B range, the SU-100 cannot be used to selectively measure UV-B radiation. The SU-100 is
sensitive to UV-B radiation, but it is included with the UV-A radiation to provide a total measurement of UV radiation.
In addition to naturally occurring UV radiation from the sun, there are many electric light sources that emit UV radiation (e.g.,
cool white fluorescent, metal halide, mercury arc, and germicidal lamps). Although the relative wavelengths of UV radiation
differ among sunlight and electric lights, the error estimates shown in the table below indicate that the SU-100 provides
reasonable estimates of UV radiation coming from electric lamps (table provides spectral error estimates for UV radiation
measurements from radiation sources other than clear sky solar radiation). For common lamps, the error is less than 10 %.
The SU-100 is particularly useful for determining the UV filtering capacity of the transparent plastic and glass barriers that are
commonly used below electric lamps.
5.0 µmol m
s
per mV) * Sensor Output Signal (mV) = UV (µmol m
-2
-1
*
s
-1
Sensor Output
35 mV
-2
s
-1
per mV
35
=
Example of UV measurement with an Apogee UV sensor. Full sunlight yields
UV radiation on a horizontal plane at the Earth's surface of approximately
175 µmol m
-2
s
-1
. This yields an output signal of 35 mV. The signal is
converted to UV radiation by multiplying by the calibration factor of 5.0
µmol m
-2
s
-1
per mV.
-2
s
-1
s
)
-2
-1
175
10
: