Calculating Irradiance from BPW21R Photodiode Current

In summary, the conversation discussed using a BPW21R photodiode in a pyranometer circuit and how to calculate irradiance from the current produced in a transimpedance amp circuit. The question of using the sensitivity value in nA/lumen to obtain an A/W value was also brought up. It was suggested to contact Vishay for confirmation on the compatibility of the BPW21R with the BPW21, and the calculation for irradiance was provided as Sensitivity x lumens/Watt * Area^-1.
  • #1
pochd
2
0
I am using a BPW21R photodiode to measure irradiance instead of a BPW21 photodiode in a pyranometer circuit that could be found in the pdf link below. How should I calculate irradiance(W/m^2) from the current produced in a transimpedance amp circuit if there is no Spectral sensitivity(Ampere/Watt) value given?


Is it ok to use the sensitivity value (nA/lx) given in the optical characteristics to get an A/W value? (0.81) Below is the calculation i used:

Sensitivity x lumens/Watt * Area^-1

9x10-9 [A*m^2/lumen] x 683 [lumens/Watt] x (7.5x10-6)^-1 [m^2]

Pyranometer Circuit Design

http://www.mdpi.com/1424-8220/9/6/4615/pdf

Photodiode Datasheet

http://www.vishay.com/docs/81519/81519.pdf
 
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  • #2
Pochd,

Welcome to PF!

You can contact Vishay, but I am 99.9% certain the "R" simply denotes RoHS compliance, functionally it should be 100% compatible with the BPW21.

Fish
 
  • #3
Pochd,

Welcome to PF!

You can contact Vishay, but I am 99.9% certain the "R" simply denotes RoHS compliance, functionally it should be 100% compatible with the BPW21.

Fish
 
  • #4
Any comments on the calculation of irradiance using the nA/lumen value?
 

1. How is irradiance calculated from BPW21R photodiode current?

The irradiance is calculated by using the equation Irradiance = Photodiode Current / (Sensitivity x Area). The sensitivity is a constant value provided by the manufacturer and the area is the size of the photodiode's active region. This equation is based on the principle that the current generated by a photodiode is proportional to the amount of light incident on it.

2. What is the sensitivity of the BPW21R photodiode?

The sensitivity of the BPW21R photodiode is typically around 0.45 A/W (Amps per Watt). This value may vary slightly depending on the specific model and manufacturer.

3. Can I use the same sensitivity value for all wavelengths of light?

No, the sensitivity of a photodiode is dependent on the wavelength of light that it is detecting. The sensitivity value provided by the manufacturer is usually for a specific wavelength, so it is important to use the correct value for the wavelength of light being measured.

4. Is the area of the photodiode important for calculating irradiance?

Yes, the area of the photodiode's active region is a crucial factor in calculating the irradiance. The larger the area, the more light it can detect and the higher the photodiode current will be. It is important to know the area to accurately calculate the irradiance.

5. Are there any other factors that can affect the accuracy of irradiance calculations from photodiode current?

Yes, there are other factors that can affect the accuracy of irradiance calculations. These include temperature, dark current, and linearity of the photodiode response. It is important to take these factors into consideration and make any necessary adjustments to ensure accurate calculations.

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