How do you measure or detect an excess of UV light? - Page 1
Forum section: electronics / general

author: Artlav
author_rank: Frequent Contributor
timestamp: June 26, 2015, 10:57:39 pm
content: Let's say i have an arc lamp which have some UV light in it's spectrum. You can smell ozone when it's running.I built it into an enclosure, made of what i think is UV absorbing acrylic.Question is - how can i be sure that the thing is now eye-safe?How to detect a presence of excessive UV light?I suspect there should be some sort of an instrument for this, kind of like a lux meter. If so, what is it called and where to get one?Otherwise, what other ways of detecting it is out there?I was thinking something along the lines of getting some wood's glass or similar UV pass filter, and looking for phosphorecense in something like white LED coating when light shine through it.Could that work?

author: Stonent
author_rank: Super Contributor
timestamp: June 26, 2015, 11:09:07 pm
content: Certain things like tonic water fluoresce under uv light. So if you can obtain some chemical that lights up under uv you can see if any gets through.

author: TerraHertz
author_rank: Super Contributor
timestamp: June 27, 2015, 12:09:38 pm
content: The magic ebay word is spectrophotometer. Lots and lots of them.The tricky part is finding one that can measure an external light source, rather than being a transmission spectrophotometer, which pass light from an internal broad-spectrum light through a sample to measure its absorption characteristics. Also to get one that definitely extends up into the far UV, since that's what you are worried about.

author: onlooker
author_rank: Frequent Contributor
timestamp: June 27, 2015, 12:28:14 pm
content: You may try something likehttp://www.amazon.com/Invisible-Ink-Pen-Uv-Light/dp/B006O35DW2It may not be quatitative, but it's cheap.

author: TheAmmoniacal
author_rank: Unknown
timestamp: June 27, 2015, 12:29:43 pm
content: UV sensor modules for the arduino are cheap and plentiful, might be of use?http://www.cutedigi.com/blog/use-uv-sensor-with-arduino/

author: Artlav
author_rank: Frequent Contributor
timestamp: June 27, 2015, 10:29:27 pm
content: After trying some things, i think i found a way that works.Namely, a UV-pass filter and a white LED as a fluorescent material.Here is what came out of it:(Talking in a video is soooo weird, whatever Dave thinks about it)Thanks all for suggestions!Quote from: TerraHertz on June 27, 2015, 12:09:38 pmOf all costs and sizes...Thanks for the name, ill be looking for one for sure.Quote from: TheAmmoniacal on June 27, 2015, 12:29:43 pmGreat, and i was looking for UV photodiodes at Digikey.Starting from $200 apiece.

author: lapm
author_rank: Frequent Contributor
timestamp: June 28, 2015, 12:53:36 am
content: Depending on wavelenght you might be able to use magic markers, most f them light up on uv nicely...that is assuming you are just interested if there is uv-wavelenght present or not...

author: Someone
author_rank: Super Contributor
timestamp: June 28, 2015, 02:41:30 am
content: Determining if a certain non laser source is eye safe is non trivial, you need a full spectral energy distribution which is normalised to a calibrated source, it is very expensive to buy and operate such equipment. Using filters will only check narrow parts of the spectrum and unless you have a filter and detector combination with a sensitivity following to the eye safe weighting curve (these do not exist as far as I know) it wont be giving a useful figure.

author: SeanB
author_rank: Super Contributor
timestamp: June 28, 2015, 08:32:59 am
content: If you are going to use the diffuser use a backing sheet of the clear as well, to absorb the blast of the lamp failing. Just remember that you will find the diffuser sheet goes brittle and discolours with time as the UV light degrades it.

author: eas
author_rank: Frequent Contributor
timestamp: July 01, 2015, 03:04:37 am
content: The issue with the different camera filters is a hint that your UV sensor may not be up to the task you are using it for. If it were me, I'd want more confidence that the LED phosphor is sufficiently sensitive to the different UV wavelengths emitted by the lamp.

author: TerraHertz
author_rank: Super Contributor
timestamp: July 01, 2015, 09:49:09 am
content: Heh. That's not an arc lamp. THIS is an arc lamp.I have the supply and starter and parabolic reflector for this too. But am not going to try running it till my spectrometer is fixed. For the same concerns you have, but multiplied... a bit.

author: Artlav
author_rank: Frequent Contributor
timestamp: July 01, 2015, 11:24:12 am
content: Quote from: TerraHertz on July 01, 2015, 09:49:09 amHm, i'm not concerned about the small one.I'm concerned about the BIG one -http://orbides.org/page.php?id=1003It's a big box of sunshine that is unsafe for so many reasons that adding another one is a bad idea.On the other hand, UV is hardly a concern since i'm not going near it without safety glasses anyway, and they block all of it.

author: TerraHertz
author_rank: Super Contributor
timestamp: July 01, 2015, 11:57:13 am
content: Ah ha, that's more like it.Mine are Ushio UXL-5000HN x6 (used) 4200W 30V 100-140A 1000HrsI'm not sure what to use them for either. The supply is far too heavy to lift and requires 3-phase power. Which I have in my workshop, but it's kind of limiting. Can't use for practical jokes out in the bush, party lighting, etc. Oh well.Incidentally the electrodes are solid tungsten. I have the bits from a broken one and it's quite surprising to feel the weight of a big lump of tungsten like that.I suspect that once I have my vacuum and gas scavenging system going, I'll be salvaging the Xenon from a few of them. If I can figure out how... Some of them are definitely past EOL, but Xenon is Xenon.

author: Ian.M
author_rank: Super Contributor
timestamp: July 01, 2015, 01:36:14 pm
content: Quote from: TerraHertz on July 01, 2015, 11:57:13 amHmmmm . . . .Put it in a vacuum chamber, pump it down and crack the envelope with a solenoid striker with a sharp carbide tip? Maybe wrap the bulb in aluminium foil and put in a metal can inside the chamber with only a small area of glass exposed for the striker to contain the debris and make cleanup easier.

author: Artlav
author_rank: Frequent Contributor
timestamp: July 01, 2015, 02:56:03 pm
content: Quote from: Ian.M on July 01, 2015, 01:36:14 pmBad idea.There are quite a few of such bulbs on display here and there, with the gas removed.I heard they were cutting or heating off the fill nipple until the gas started leaking out, resulting in an intact bulb with no gas inside.Something along these lines should work for getting the gas out inside a vacuum chamber as well, rather than risk ruining it by letting the bulb blow up inside.

author: Ian.M
author_rank: Super Contributor
timestamp: July 01, 2015, 03:12:25 pm
content: If preserving the bulb for display is a constraint, then I agree the fill nipple is the best place to attack. However cracking it or heating it under vacuum while maintaining a hermetic seal to your gas scavenge system is likely to be very difficult. The apparatus would have to be customised for each different bulb type and although a 25 atmosphere pure Xeon fill in a large bulb is theoretically at least quite valuable, I doubt its cost-effective to recover unless you have several bulbs of the same type

author: Someone
author_rank: Super Contributor
timestamp: July 01, 2015, 09:25:06 pm
content: Quote from: Artlav on July 01, 2015, 11:24:12 amAgain you are on the right track but missing the details. Safety glasses will block a lot of the UV but not all of it, and the other exposed parts of your body will still be getting a dose. Just relying on air attenuation of the deep UV is a bad idea when you are either close to the source, or scaling up the power.

author: Red Squirrel
author_rank: Super Contributor
timestamp: July 02, 2015, 04:58:07 am
content: Do those produce UVA or UVB? I wonder if that could kill off psoriasis lol. I'd totally try it with proper blackout eye wear.

author: TerraHertz
author_rank: Super Contributor
timestamp: July 02, 2015, 05:35:34 am
content: Quote from: Ian.M on July 01, 2015, 03:12:25 pmLetting the Xenon out of the bulb (whether breaking or preserving the lamp) is the least of the obstacles. The main problem is how to transfer all the gas (from several lamps) to a storage cylinder, without contaminating it.Pumping down the chamber and tank to a good vacuum is easy, then you'd close off the chamber from that pumping system. Then open the lamp(s). Bearing in mind vacuum chambers tend to be not rated to hold internal pressure above 1 atm. At least mine isn't. The seals rely on external pressure.And then... ?I have a big vacuum chamber, vacuum pumping system, and some suitable storage tanks. Fine capillary pressure tubing (to minimize wasted volume) I can arrange.But am having no luck at all finding some kind of high pressure gas transfer pump, that can also scavenge down to near vacuum on the source side.It's not just for these lamps. It's a generic problem I need to solve for other uses as well.Transferring relatively small volumes of gas, from one container to another without contamination, with potentially high pressures at ether end. How is it done?Something like this I suppose, plus a vacuum system for preparation:http://au.alibaba.com/product/100937005-High-Pressure-Liquid-Gas-Transfer-Pump.htmlbut preferably electrical drive.Edit: Btw, a caution about handling those big lamps. The safety instructions I've seen recommend wearing full body protection against glass shrapnel. The chunks supposedly can cut deeply enough to reach major arteries.All mine are in safety shells. Except very briefly for photos, and I'm slack so don't bother with the protective gear then. If I was setting one up to use it, I would wear full leathers and face protection.Incidentally, does anyone here recognize this gas tank? It's a kind of special thing.

author: Ian.M
author_rank: Super Contributor
timestamp: July 02, 2015, 05:49:44 am
content: If you can chill the receiving cylinder enough Xenon will liquify or even solidify removing the high pressure pump requirement. You'd need liquid nitrogen though as dry ice isn't cold enough.

author: helius
author_rank: Super Contributor
timestamp: July 02, 2015, 06:00:07 am
content: Quote from: TerraHertz on July 02, 2015, 05:35:34 amLooks like a gas bottle from an aircraft or rocket?

author: G7PSK
author_rank: Super Contributor
timestamp: July 02, 2015, 07:31:12 am
content: Also looks like the gas globe from a Citroen suspension system.

author: TerraHertz
author_rank: Super Contributor
timestamp: July 02, 2015, 07:43:21 am
content: Quote from: Ian.M on July 02, 2015, 05:49:44 amHmm. Not bad. Except I'd be wary about chilling a tank that also has to hold high pressure at room temp. For fear of doing bad things to the ductility. Also the cost, and nuisance of having to order liquid nitrogen each time.Also won't work for oxygen, and other gasses. So not a general solution. Well, it would work for nitrogen, but kind of pointless.Quote from: helius on July 02, 2015, 06:00:07 amNope. Wrong kind of valve and attachment. Same kind of over-the-top construction though. The tank is either stainless or titanium, I'm not sure which and am not going to grind it a bit to see the sparks color. The valve is stainless.G7PSK, Citroens have 3000 PSI tanks?I do know what it is. Waiting to see if anyone can guess.

author: SeanB
author_rank: Super Contributor
timestamp: July 02, 2015, 05:44:29 pm
content: It is a 5 minute emergency O2 supply for sure, but the valving is wrong for aviation so likely it is an emergency supply for an anaesthetic unit, where you really do not want to have the main O2 supply drop out in use, while you still have to supply a patient with breathing air while either getting a backup source active or stopping the operation and weaning them off the main anaesthetic gas.

author: TerraHertz
author_rank: Super Contributor
timestamp: July 04, 2015, 07:45:45 am
content: It's the oxygen tank from a MK-16 UBA. 'Underwater Breathing Apparatus' US Navy spec-ops rebreather dive system.http://www.globalsecurity.org/military/library/policy/army/fm/20-11/chap17.pdfClosed-Circuit Mixed-Gas UBA Divinghttp://www.alohashoredivers.com/links/DiveMan_rev6_vol4.pdfClosed Circuit and Semiclosed Circuit Diving Operationshttp://www.dtic.mil/dtic/tr/fulltext/u2/a091892.pdfMK 16 MOD 0 UBA. TECHEVAL REPORT. JULY 1980Three of them, brand new in sealed bags, sent to the garbage dump by our brilliant military, only a few years after manufacture. I know how that happened, and it's typical. A 'certain military stores establishment' had a policy that any stock line on the shelves that doesn't have any supply requests for one (or was it two? I forget) years, gets dumped. Literally.That was back in the early 2000s. No idea if the situation is unchanged.I shudder to think what these tanks cost to buy. Our taxes at work.Anyway, they'll do nicely for experimental gas mix storage.

author: SeanB
author_rank: Super Contributor
timestamp: July 05, 2015, 10:31:07 am
content: Our military keeps things for ever, as they actually have had to fight a war.........