Ocean Optics CHEM2000 - Manual (Page 26)

3: Experiment Tutorial
Note
If at any time any sampling variable changes – including integration period, averaging,
boxcar smoothing, distance from light source to sample, etc. – you must store a new
reference and dark spectrum.
Relative Irradiance Experiments
Irradiance is the amount of energy at each wavelength from a radiant sample. In relative terms, it is the
fraction of energy from the sample compared to the energy collected from a lamp with a blackbody
energy distribution, normalized to 1 at the energy maximum. Relative irradiance is calculated by the
following equation:
S
(
λ
- D
λ
I
λ
=B
λ
R λ
- D
λ
)
Where:
B = R elative energy of the reference calculated from the color temperature ( in Kelvin )
S = Sample intensity at wavelength λ
D = Dark intensity at wavelength λ
R = Reference intensity at wavelength λ
Common applications include characterizing the light output of LEDs, incandescent lamps and other
radiant energy sources such as sunlight. Also included in irradiance measurements is fluorescence, in
which case the spectrometer measures the energy given off by materials that have been excited by light at
a shorter wavelength.
Note
The components that came with the Maxwell will not allow you to make relative
irradiance measurements. To make relative irradiance measurements, the reference
spectrum must be made in Scope Mode with a blackbody light source of known color
temperature. This color temperature is needed in order to calculate relative irradiance.
The light source that comes with the Maxwell is not a blackbody light source with a
known color. To purchase a blackbody light source and other necessary hardware, contact
Ocean Optics.
► Procedure
To take a relative irradiance measurement:
1. Select Spectrometer | Spectrometer Configuration from the menu. Next to Color Temp, make
sure the color temperature in Kelvin of the reference lamp you are going to use is entered here.
Click OK.
20 PRELIMINARY DRAFT 105-00000-CHM-02-0405