Labels on consumer products are usually intended to scare the consumer so they don't open the product, rather than to use the correct terminology, so they often state something like "Danger - high voltage inside" when the voltage does not exceed LV.
LED Lights in bathroom over shower
- Thread starter steveb1964
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Indeed, and that was my very point - that, when communicating with the general public, one needs to realise that, to very many of them, 'high voltage' implies danger, whereas 'low voltage' implies 'no real danger' - which is why I think that trying to 'educate' them to use what to them is 'illogical' (even if 'correct') terminology is bound to cause (potentially dangerous) confusion.
I don't know the history of the official definitions of voltage bands, but I rather suspect that the general public's believ that 'low voltage'=safe was probably pretty well-established before the 'official' terminology was introduced!
Kind Regards, John
I don't know the history either, but it was before 1969 from a standard of that date I was looking at.
If you wanted to change the definitions so that LV meant 'safe', what voltage would you set as the upper limit though? I remember some evidence was presented to the European Commission that voltage far less than the 50V limit for ELV could be fatal under some circumstances.
If you wanted to change the definitions so that LV meant 'safe', what voltage would you set as the upper limit though? I remember some evidence was presented to the European Commission that voltage far less than the 50V limit for ELV could be fatal under some circumstances.
The general public's belief that low voltage was 'safe' and 'high voltage' was 'dangerous' certainly existed in the early 60s (when I started 'playing with electricity'!), and I would suspect that had been the case for many previous decades. At that time, we regarded 90V 'High Tension' batteries as being 'dangerous high voltage', and (usually!) treated them with considerable respect.
That's would obviously be open to debate/discussion, based on whatever evidence existed, but I would have thought that 50V is probably not an unreasonable threshold - although not impossible, it would be incredibly unusual for 50V or less to prove fatal to an adult human being.
Kind Regards, John
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Everything that's been said is true, but unless you can successfully lobby for a change to official definitions, and a change to the way that the law is worded, you have to take every opportunity you can, no matter how slow/difficult it will be to effect a significant change, to tell people what LV and ELV actually mean.
Yes - but as I said, the beliefs of much of the general public's are so well-entrenched that such an exercise is likely to be ineffective or, at best, extremely slow, and the confusion would persist for the decades that such a process would probably take. Indeed, as below, the confusion would probably increase during and throughout such a period of 'education'
Although my personal view is that the 'official' definition of LV should never have been allowed to arise, there would probably be considerable resistance to any attempt to change that definition now that it has become well-established.
Ironically, the education you suggest (and the well-intentioned attempts to provide such education in places like this) could actually make the confusion/ambiguity much worse. At present, I think you'd have to look very hard to find an ordinary member of the general public who would describe a 230V/240V item as 'low voltage' (virtually none of them will even be aware of that official definition) - so we can be all-but-certain that, when they speak of 'low voltage', they mean ELV. However, if your campaign succeeded in getting an appreciable proportion of the population 'educated', we wouldn't have a clue what a particular member of the public meant when they spoke of 'low voltage'.
If it were happening (and, thankfully, it doesn't seem to be) I think the one thing that (at least for the next few decades) we would have to seriously consider 'banning' (despite 'official definitions') would be having any mention of 'low voltage' on any consumer product which was not actually ELV.
Kind Regards, John
They do - and I assume that is because of the different physiological responses to AC and DC shocks. However, that's probably of no real importance to this discussion, since the general public (and most others) are probably rarely going to come across DC voltages between 50V and 120V.
Interestingly, as I recently wrote, back in the 60s we regarded 90V "HT" batteries as producing a "dangerous high voltage", even though (now, and probably still then), that is, officially, very much 'ELV'.
Kind Regards, John
Eh?
What's the problem? ELV goes up to 120V DC, doesn't it? ... or it is something else you're questioning?Eh?
Kind Regards, John
Ooops!
In my world (machinery) ELV limit is 50V ac or dc.
In my world (machinery) ELV limit is 50V ac or dc.
AhaOoops!
... but this is then getting even more ridiculous, isn't it? It's bad enough for the official terminology to be confusing to, and not understood by, most of the population, but you now appear to be saying that the definitions of that terminology are not even consistent across industries!
Kind Regards, John
The difference is due to the fact that it is not as simple a saying that a voltage below X volts is safe. We have to consider that area of contact, the likely skin resistance, the age of the person involved, the disconnection time of the protective device, the current path through the body, etc. Usually we only consider the onset of ventricular fibrillation in adults, and select a value that will not cause fibrillation in 95% of adults.
In some applications the 'safe' values can be very much lower that 50V. I can't find the paper at the moment, but I'm aware of a fatality caused by a voltage in single digits, in a child undergoing dialysis.
In some applications the 'safe' values can be very much lower that 50V. I can't find the paper at the moment, but I'm aware of a fatality caused by a voltage in single digits, in a child undergoing dialysis.
Sure, I can fully understand and accept all that, but I wasn't talking about what voltage was safe - I was talking about definitions of "ELV" (hence, by implication, the lower bound of "LV"). Maybe I misunderstood you but I thought you were saying that, in the context of machinery, the definition of ELV stopped, and the definition LV therefore started, at 50V DC. Did I misunderstand?
Indeed. Particularly if there is an electrical path to the contents (blood or artificial fluids, all of which are pretty conductive) of intravenous (or other) cannulae, catheters or lines (such as likley to be present in someone undergoing dialysis), then tiny voltages can precipitate rhythm disturbances in the heart, which have the potential to be fatal. However, again, that's to do with 'safe voltage levels', not the definitions of LV and ELV. Having said that, DC is, by its nature, generally much less likely to precipitate serious rhythm problems in the heart than is AC (and, ironically, 50Hz AC is not far off being the 'most dangerous' frequency).
Kind Regards, John
Sorry, I should have said 60V DC. We don't actually define the voltages, but there are requirements that apply when using PELV to achieve protection against electric shock. Those requirements include 25 V ac and 60 V dc.
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