BITD life was simple: if a box didn't have any voltage that could exceed
60V, even in fault conditions, it counted as Safety Extra Low Voltage (SELV) and you didn't have to worry about electric shock.
Those days are gone--now the rules apparently center on the available energy, with many many special cases.
Anybody here have recent experience with UL certification?
Thanks
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510
http://electrooptical.net
https://hobbs-eo.com
Yup, us too, except that we've standardized on 24V because that way the boxes are harder to blow up. ;)
I'm mainly thinking about that APD power supply. It has three separate current limit circuits, so it can't go above 5 mA unless they're all broken, but it goes up to 250V.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510
http://electrooptical.net
http://hobbs-eo.com
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| STV, Queen Creek, AZ 85142 Skype: skypeanalog | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
Thinking outside the box... producing elegant solutions,
by understanding what nature is hiding.
"It is not in doing what you like, but in liking what you do that
is the secret of happiness." -James Barrie
I don't know, but I've got similar voltages. I think we mostly try to stay within the letter of the law, but don't get any certification. (Or if you are small enough can you self certify? Sounds like an oxymoron) We've been selling our diode laser for years. ~120V DC going to a piezo stack. When we started shipping to Europe we added 'security' screws to one end of the DB9 connector so that some idiot wouldn't take it off and stick his finger in there. Hmm I should probably think about adding current limit to the line.... it's got a series resistor but a depletion Fet thing might be better.
OK, I think someone (in the EU) wanted a CE mark, and so that's what we did. In the more distant paste there was a German professor who wanted to make sure our Rb lamps passed emission standards. I went with a guy and we ran the tests.. not certified, but just measured stuff, found that there was a bit of radiated gunk above 1 GHz... we made the light hole a little smaller, (actually not a big deal) and then the Prof. didn't even buy one!
BITD a relative of mine tested a 67.5-V B battery that way. Only once. ;)
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510
http://electrooptical.net
http://hobbs-eo.com
Without seeing the exact UL wording I very much doubt it is an issue about electric shock,
Even for ELV circuits, large currents can do a lot of damage, I would not us rings or metallic watch bands e,g, when working with a ELV forklift battery, Specifying the energy available instead of current available also solves the issues of big (super)capacitors.
At least in EU, there are some situations in which ELV (PELV/SELV) can be "dangerous voltage".
With pretty clammy hands, I grabbed two alligator clips in opposite hands and cranked up the DC voltage. It got pretty bad about 90 volts. I noticed the same metallic taste afterwards.
--
John Larkin Highland Technology, Inc
picosecond timing precision measurement
jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com
When I was 17, I took a year off university and worked in a camera shop, among other things. (I'd goofed off pretty badly in my first year, so I decided to come back to it when I could take it seriously.)
With some of my pay, and an employee discount, I set up a darkroom in my parents' furnace room. It was hot air heat, which stirs up a lot of dust--_not_ what you want in a darkroom. So I attached a hose and nozzle to the drain spigot of the hot water tank, and before using the enlarger I misted down the table, concrete walls, and floor. Worked great. Then one time I reached up to turn on the suspended light bulb in the middle of the ceiling, and couldn't let go. I had to let my knees bend to the floor to pull my hand free. A good thing the wire didn't come down. Needless to say, a very beefy ground wire was attached to the fixture very shortly after.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510
http://electrooptical.net
http://hobbs-eo.com
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