Calculating Irradiance from BPW21R Photodiode Current

AI Thread Summary
The discussion focuses on calculating irradiance (W/m^2) from the current produced by a BPW21R photodiode in a transimpedance amplifier circuit. Users are questioning whether the sensitivity value in nA/lumen can be converted to A/W for this purpose, given the absence of a direct spectral sensitivity value. A proposed calculation method involves using the sensitivity, lumens per Watt, and the area of the photodiode. Additionally, it is confirmed that the BPW21R is functionally compatible with the BPW21, primarily differing in RoHS compliance. The conversation emphasizes the need for clarity on the conversion method for accurate irradiance measurement.
pochd
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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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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
 
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
 
Any comments on the calculation of irradiance using the nA/lumen value?
 

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