Irradiance measurement procedure

In summary, the speaker is proposing a method to capture the sun's spectrum with a filter and then transform the data to remove the filter's effect. They also mention potential limitations with this approach, such as amplifying noise and the need for a specific type of filter.
  • #1
elegysix
406
15
Here's what I'm thinking. The sun is too bright to measure directly with our equipment. If I calibrate without a filter, and capture the reference spectrum with and without the filter, then I can model how the filter changes the spectrum. This way I can capture the sun spectrum with the filter, and transform the data as if I had not used it.

What I mean to say is, if
[itex]I_{r}(\lambda)=Y(\lambda)[/itex]
and
[itex]I_{r+f}(\lambda)=G(\lambda)Y(\lambda)[/itex]
then is it valid to argue that
[itex]I_{s}(\lambda)=\frac{I_{s+f}(\lambda)}{G(\lambda)}[/itex]

Or is it that [itex]G(\lambda)[/itex] is dependent on I?

where
[itex]I_{r}[/itex] is the irradiance of the reference
[itex]I_{r+f}[/itex] is the irradiance of the reference measured through a filter
[itex]I_{s}[/itex] is the irradiance of the sample
[itex]I_{s+f}[/itex] is the irradiance of the sample measured through the same filter
 
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  • #2
As a first approximation, that approach is fine. The main shortcomings with this approach are 1) if G(λ) << 1 (the filter transmits very little light at some wavelengths) and/or 2) if your detector is a coarse-grained spectrometer (say a color camera). Problem (1) introduces error by amplifying noise, and problem (2) means that the measured spectrum is a convolution, not a multiplication, so the 'division' step is actually a deconvolution.

The filter transmittance should not vary with intensity unless it has been specifically designed to do so (e.g. a saturable absorber).
 
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1. What is irradiance measurement procedure?

Irradiance measurement procedure is a scientific method used to quantify the amount of radiant energy received on a surface per unit area. It involves the use of specialized instruments such as radiometers and spectroradiometers to measure the intensity of electromagnetic radiation.

2. Why is irradiance measurement important?

Irradiance measurement is important because it helps us understand the amount of energy received from the sun or other sources of radiation. This information is crucial for various fields such as solar energy, agriculture, and environmental monitoring.

3. What are the units used for measuring irradiance?

The units used for measuring irradiance depend on the type of radiation being measured. For solar radiation, the most commonly used unit is watts per square meter (W/m2). For other types of radiation, units such as joules per square meter (J/m2) or watts per square centimeter (W/cm2) may be used.

4. What factors can affect irradiance measurements?

The accuracy of irradiance measurements can be affected by several factors, including the type of instrument used, its calibration, the angle of measurement, atmospheric conditions, and the presence of shadows or other obstructions. It is important to carefully consider these factors when conducting irradiance measurements to ensure accurate results.

5. How is irradiance measurement procedure performed?

The procedure for irradiance measurement may vary depending on the specific application and instrument used. However, it generally involves calibrating the instrument, placing it at the desired location and angle, and recording the measurements over a period of time. These measurements can then be analyzed and compared to other data to draw conclusions about the amount of radiation being received.

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