In message <[log in to unmask]> "scott kivi" writes:
> With UV exposure units the intensity of the lamps is measured 
> with a radiometer. In our imaging departments, we keep a close eye on 
> our exposures as far as intensity. However we've been overlooking an 
> equally important factor, UV wavelength, and the radiometer doesn't 
> measure that.  I am looking for a practical method of measuring and 
> monitoring the wavelength of the lamp as it degrades. If anyone can 
> steer me in the right direction or has any input on this matter, I 
> would appreciate talking with you.

My experience is with UV curing lamps, not exposure lamps. I hope that the same 
thoughts apply.

Lamps produce a spectrum of electromagnetic radiation, from short wave UV 
(which is what I think you are interested in), to infra red (IR... heat!). 
Since you cannot see UV light with the naked eye, but I bet you can tell 
whether your lamp is on or not by eye, it produces some "blue" visible light as 
well. The proportion of the total lamp power which is emitted at each 
wavelength is a matter of lamp design. 

As you know, curing lamps which are based on arc lamp technology will 
deteriorate with age. However, the wavelengths do not change, just the 
intensity at each wavelength. The radiomaters which we use measure the 
intensity of the UV light _at a particular wavelength_. In our case, the most 
useful wavelength is 365nm. In your case, I would guess that your radiometer 
measures the intensity at a shorter wavelength, say ~250nm. More expensive 
radiometers will measure the intensity at different wavelengths, but, for 
example, you need to change the sensor. 

The material which you are curing or "UV drying" will react to one (or more) 
wavelengths of UV light, and will cure faster with higher intensities at that 
wavelength. All you need to do is determine from the material supplier which 
wavelength(s) is the critical one, make sure that your radiometer is measuring 
that wavelength, and keep tabs on the intensity of that wavelength. Establish a 
minimum intensity at which your process is still satisfactory, change bulbs 
when it gets below this.

Sounds like you are doing this already.
Peter
...............................................................................
Peter Swanson                                              Oxfordshire, England
INTERTRONICS
[log in to unmask]                              Compuserve: 100120,3641
           http://ourworld.compuserve.com/homepages/Peter_Swanson

    Confidence is the feeling you have before you understand the situation.
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