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Peter Offline OP
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Has anybody had issues with Class II TV's in patient areas. We found 80-100V @ 200ua on the screen of the headphone socket.
Acceptable in Class II, but no good in patient areas ie renal.
If you have accountered this how did you solve it?

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Super Hero
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As we all know, there are "Codes" about patient areas, what constitutes them, and what leakage currents etc. are allowable in the various "zones", and all the rest.

But, maybe you need to explain a little further here, Peter. I am imagining ceiling mounted TV sets in a dialysis setting (that is, with the TV set outside the "patient safety zone", as it were). So, where is this headphone socket, exactly?

The "answer" here could well be Bluetooth, I would have thought. smile


If you don't inspect ... don't expect.
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Peter Offline OP
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Yes Geoff ceiling mounted TV's but the headphone outputs fed to a plastic wall trunking with a short flying lead stereo socket coming out. The solder type with a metal screwed mount and a plastic cover. We thought RF/IR ,but there are eight others on the unit which could interfere with each other.

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Super Hero
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Interesting. I've heard that there are TV sets available now with Bluetooth audio capabilities (that is, for use with Bluetooth headsets). I don't know whether you can have headsets "tuned" to individual TV sets, though (but this would be possible technically, of course). Otherwise, why not get a single massive plasma TV (only joking)?

The other way to look at the problem, I guess, would be to think about providing isolation at the stereo socket end (an isolation amplifier). Something for you to have a go at, perhaps? But as you obviously know the exact requirement, with that in mind maybe you could spend a fruitful ten minutes or so on Google! smile

Can't that screening be earthed, by the way?


If you don't inspect ... don't expect.
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Peter Offline OP
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We had thought about earthing the screen, but we would may need to check with manufacturer as this would probably upset the filtering on the switch mode psu (likely cause of the problem!)The other thoughts are audio isolation transfomers or the old type air tube headsets, the problem with that they are mono only.

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Super Hero
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Super Hero
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Yes, as is often the case, once you starting taking a close look at things like this, there is more to it than meets the eye. You have to look a the big picture (What? With plasma TV? My Goodness, the puns are coming fast and furious this afternoon)!

Now you've got me wondering how you get on with regular patients (with dialysis of course being the outstanding example) bringing in their own stuff. Especially if it's mains powered, that is.

Have you considered the Risk Assessment approach* to this one, I wonder. That is, is there really a problem here at all? smile

* aka a "get out"!


If you don't inspect ... don't expect.
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Hero
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Earth the headphone socket.


If you think hiring professionals is expensive, try hiring amateurs!
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Super Hero
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Yeah, best try that first! smile


If you don't inspect ... don't expect.
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bam Offline
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I think you might have opened a new can of worms!
There are lots of problems associated with the use of switch mode power supplies, as the output often floats at about 50% of the input voltage. ANY smps's used in patient areas should comply with 60601. I have a voltstick that I run over all such things as a quick check. That includes laptops, mobile phone chargers and so on. Some of these things can pack quite a punch.
If patients are allowed to bring these sort of things in, perhaps you need to think about how you deal with the problem!

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Super Hero
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I couldn't agree more, Brian. Let's have the debate!

Canned worms are many and various (57 Varieties?), and even better now that so many come with a ring-pull!

After all, what's the point of all our endless hand-wringing over this and that esoteric leakage current as regards to electro-medical equipment (and the environment it's used in), when Little Johnny (oh, I guess I mean Jason there ... whatever) is sitting up in bed in the kid's ward twiddling away with his [insert latest "must have" that also has a power brick], and Old Gran in the stroke unit (or whatever they're calling it this week) has all her old favourites blaring out (at max. vol) from her old mains radio (cassette player, portable TV, whatever).

I guess I should also mention the guy in CCU who just has to carry on "working" (with his laptop, that is) ... oblivious to the fact that that is how he came to be in there in the first place!

Yes, every biomed should carry a Volt Stick in their shirt pocket (just as long as it's one of the original, yellow ones, that is). smile


If you don't inspect ... don't expect.
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