Calculating Irradiance from BPW21R Photodiode Current

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SUMMARY

The discussion focuses on calculating irradiance (W/m²) from the current produced by a BPW21R photodiode in a transimpedance amplifier circuit. The user proposes using the sensitivity value of 0.81 nA/lx to derive an A/W value for the calculation. The formula applied is Sensitivity x lumens/Watt x Area^-1, utilizing specific constants such as 9x10^-9 A*m²/lumen and 683 lumens/Watt. The BPW21R is confirmed to be functionally compatible with the BPW21, with the "R" designation indicating RoHS compliance.

PREREQUISITES
  • Understanding of photodiode operation and characteristics
  • Familiarity with transimpedance amplifier circuits
  • Knowledge of irradiance measurement principles
  • Basic proficiency in unit conversions (A to W, lumens to watts)
NEXT STEPS
  • Research the calculation methods for irradiance using photodiodes
  • Explore the datasheet for the BPW21R photodiode for detailed specifications
  • Learn about transimpedance amplifier design and its applications
  • Investigate the implications of RoHS compliance on electronic components
USEFUL FOR

Electrical engineers, optical engineers, and researchers involved in photodiode applications and irradiance measurements will benefit from this discussion.

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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