Hi,
I want to sense UVC light (a germicidal steriliser) at around 254nm to determine whether the lamp is working. I've looked at specialised sensors, reversed LED, light-dependent resistors/diodes, cameras etc. But everything is either uber expensive, or in the wrong wavelength.
Any ideas? I feel like I'm missing something as there are products like this http://www.viqua.com/product.php?p=323 but I'm not sure what approach they use...
Cheers,
Lee
Well, if the light also produces visible light (can you see when it is turned on or off?), then it is most probably producung the UV also, so a normal photo resistor might be appropriate. Will your UV light cause fluorescent materials to "fluoress"? Below is wikipedia stuff.
Germicidal lamps use quartz (glass) doped with an additive to block the 185nm wavelength. With the addition of a suitable phosphorescent coating, they can be modified to produce a UVA, UVB, or visible light spectrum.
Those are good ideas - I'll look into them. My understanding is that for sterilisation, the UV has to be at or close to 254nm, and that lamps can appear to put out a lot of visible light, but may not be putting out 254nm. Any idea what products like the one I linked use?
I found the PC5-2-TO5, which looks promising at 25USD if I can find a source...
One option would be to isolate the UV, using a filter or a spectroscope-like arrangement.
Some of my favorite optical surplus dealers who might have a suitable filter cheap: Surplus Shed, Meredith, and Laser Surplus Sales. Unfortunately, bscoptics.com came up missing: Bill was already semi-retired the last time I dealt with him (over 5 years ago), so he may have fully retired. Or maybe the server was just down for maintenance or somesuch.
Hi,
Thanks for all the suggestions above.
I have thought more about my requirements and while I believe that the UV tube will either work at 254nm, or otherwise have blown, it would be nice to be able to detect output and even intensity at 254nm specifically. This is because germicide occurs most effectively at that wavelength.
Also, I need a solution that can easily be inserted into the water line, ideally in the end cap of the steriliser.
I think all of the things suggested above will work for detecting the presence of UVC light. Others are photomultiplier tubes, flame sensors, and phototransistors. Photomultiplier tubes and flame sensors have very high voltage requirements and need to be calibrated - also they are vacuum tubes and may degrade over time.
I am going to try to source one of these http://sales.hamamatsu.com/index.php?id=13183033, and perhaps run it through an op amp, or use it reverse-biased. If I can get one at a reasonable price I'll trawl the datasheets and app notes and figure a circuit out.
Cheers,
Lee