How can I accurately measure irradiance for my UV sanitization device design?

[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.

 

[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

You can get detectors that measure irradiance. Do you need more information than that?

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).

 

[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.

NIST has a good bit of information about irradiance measurements:

http://physics.nist.gov/Divisions/Div844/facilities/fascal/fascal.html

http://ts.nist.gov/MeasurementServices/Calibrations/spectroradiometric.cfm