Calculating irradiance from lux of a halogen lamp

In summary, the group is trying to determine the irradiance hitting a steel sheet from a halogen lamp, but they can only measure the lux at the surface of the sheet. To convert lux to irradiance, the spectrum of the lamp's light is needed, which they are unable to obtain. However, there is an alternative method using an integrating sphere, which collects all of the light from the lamp and calculates the total flux to determine the irradiance on the steel sheet.
  • #1
Flucky
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Hi all. We're currently working on a project and need to know the irradiance hitting a steel sheet some distance away from a halogen lamp. The setup looks like:

n1pats.png


The problem is we can only measure the lux at the surface of the steel sheet, and I believe in order to convert lux to irradiance you need to know the spectrum of the light coming from the lamp - something we are unable to do.

Is there any alternative way of getting a reasonably accurate irradiance measurement?
 
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  • #2
Yes, you can use an integrating sphere to measure the total flux (or radiant power) emitted by the halogen lamp. An integrating sphere is a hollow sphere with a diffuse white interior surface that is designed to collect all of the light from a source and trap it inside the sphere. The total amount of light that is collected, known as the total flux, can then be used to calculate the irradiance of the light hitting the steel sheet.
 

Related to Calculating irradiance from lux of a halogen lamp

1. What is irradiance and how is it different from lux?

Irradiance refers to the amount of radiant energy that is incident on a surface per unit area. It is measured in watts per square meter (W/m²). Lux, on the other hand, is a unit of illuminance that measures the amount of visible light that is incident on a surface per unit area. It is measured in lumens per square meter (lm/m²). Essentially, irradiance measures the total amount of energy, while lux measures the visible portion of that energy.

2. How do I calculate irradiance from lux of a halogen lamp?

To calculate irradiance from lux, you will need to know the spectral distribution of the halogen lamp. This can be obtained from the manufacturer's specifications. Then, use the formula E = L x K, where E is the irradiance in W/m², L is the illuminance in lux, and K is the spectral conversion factor. This factor takes into account the spectral distribution of the light source and its effect on the human eye. The specific value of K will depend on the type of light source being used.

3. Can I use a lux meter to measure irradiance?

Yes, a lux meter can be used to measure irradiance. However, you will need to know the spectral distribution of the light source and use the appropriate conversion factor to calculate the irradiance. Additionally, make sure the lux meter is calibrated for the specific type of light source you are measuring.

4. How does distance affect the irradiance of a halogen lamp?

Distance has a significant impact on the irradiance of a halogen lamp. As distance increases, the amount of energy that reaches a surface decreases, resulting in a lower irradiance. This relationship follows the inverse square law, which states that the intensity of light is inversely proportional to the square of the distance from the source.

5. Can the irradiance of a halogen lamp be increased?

Yes, the irradiance of a halogen lamp can be increased by increasing the power or intensity of the lamp, or by moving the lamp closer to the surface being illuminated. However, it is important to note that halogen lamps have a maximum safe operating temperature, and exceeding this temperature can lead to decreased lamp life and potential safety hazards.

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