1. Feb 4, 2009

tihort

hello.

I am working to understand and design a UV sanitization device.

What is a good resource to learn about irradiance and its relation to distance from a surface.

Secondly, in real life, how is irradiance measured? Given a surface area, I would need to specify bulbs of certain intensity to get the device to work.

Thank you.

2. Feb 4, 2009

reasonableman

http://en.wikipedia.org/wiki/Irradiance has the basics. For a simple source (isotropic in all directions) it is an inverse square law (1/d^2, where d is distance) http://en.wikipedia.org/wiki/Inverse_square_law

For an actual calculation you need to know the power output of the bulbs you are getting within the wavelength band that you need (bulbs usually emit over a wide range of frequencies).

Last edited by a moderator: Apr 24, 2017
3. Feb 5, 2009

Andy Resnick

The wiki article was ok, my gold-standard reference is Wolfe's "Introduction to Radiometry".

As to your second question, it can get a little tricky- you need to know details about the bulb's radiance: how much light goes in what direction. That plus the geometry will tell you how much radiation is incident on your surface.

Irradiance detectors are a fairly standard piece of equipment, but to get highly accurate and precise (<10%) measurements requires some care- spectral characteristics, polariation control, etc. An integrating sphere combined with a stable detector can give 1% precision without too much trouble.