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How can I convert the voltage measured across a photodiode to light output or intensity or any other photonic unit? I am trying to measure the light intensity of natural light (sunlight/ambient outdoor light) using a photodiode but the photodiode measures voltage as a function of light intensity. Google isnt being any help.

Thanks

aa112
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    There are devices on sale that do this. Also delete repeat is not a good tactic on here - some of us have a good memory for repeated questions. – Solar Mike Dec 30 '22 at 09:48
  • A google search "photodiode to measure light intensity" brings up a **lot** of good results - either devices or how to build. You should be able to work with that. – Solar Mike Dec 30 '22 at 09:50
  • @SolarMike The main issue I'm having is that I need a value in lumens so that I can calculate lux across an area, but the photodiode outputs a value in volts. There's probably something obvious I'm missing, though, but that's why I'm on this site. I'm aware that devices for this, though for the project I need this for the sensor would be directly connected to the project itself (which I'm planning to do with an arduino because of its overall simplicity) so using said devices unfortunately isn't an option for me. – aa112 Dec 30 '22 at 18:51
  • @SolarMike I wasn't attempting to do delete repeat, I did delete my previous question but that was because of unrelated reasons, and the question was different, though I can see how they seem similar. Apologies if it seems that way, I'm unfamiliar with this website's etiquette/how it works in general. – aa112 Dec 30 '22 at 18:54

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Ordinary commercial photodiodes aren't calibrated to give a specific number of volts per lumen. You would need to calibrate your new instrunemt against a known good lightmeter.

As an additional problem, the definition of the lumen adjusts for the relative sensitivity of the human eye to different colours. A photodiode won't do that.

Simon B
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