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When I worked in the steel industry, all our test gear/etc was rated at 50Vrms
It had been decided any voltage greater than 50Vac was a hazard.
You can imagine the size of the 240/50v step down isolating transformers we had to haul around. Would you believe even the damn'd electric kettle was 50Vac. All the cable were as thick as your thumb, the 50V connectors, well!.
So I've always considered over 50Vac as a potential hazard.
I have a greater respect for Vdc supplies, I still have got the scars on my fingers from a 1000Vdc psu.
Its not always the 'shock' that kills you.
In you are working a confined space, just jumping back can bring you contact with lethal objects or make you fall from a height.
If you must touch a 40v psu, use the back of your fingers, any muscular contraction will pull hand away, not onto the supply.
Just my two cents... here in France, everything over 30 V is rated as unsafe... As Nigel Goodwin said, it varies from person to person (and from day to day also, your resistance varies with a lot of factors!)
So, just be be on the safe side, handle everything over 30 V with care, there is a reason why this is the maximum voltage allowable in some applications (i.e. weapon systems, RS-485 communications or the AS-i standard).
I don't think that you will get injuries or problems with "as little as" 40 V, but it may be a nasty way to find out that you have a health problem...
So let me improve on Eric Gibbs' suggestion: if you must touch a 40 V PSU, use rubber gloves.
Its not always the 'shock' that kills you.
In you are working a confined space, just jumping back can bring you contact with lethal objects or make you fall from a height.
A number of people have been killed installing/moving loft/attic aerials.
One hand on the metal cold water header tank, to steady themselves and the other hand holding the aerial. Bye!!
So screech another very important safety tip, if you don't already know, keep your left hand in your pocket
or behind your back when touching the 40Vdc.
I've gotten an uncomfortable tingle (hate electrical shocks), from my truck battery. Really can't imagine why anyone would willfully want to get shocked. When somebody says the voltages is safe, it means it won't likely kill you, by itself. You may still feel it, your reaction may be more dangerous. There are also medical conditions that can be triggered.
I guess that it is the current that kills and not the voltage.... The zaps that one get in winter is generally 2000v+
But one still gets a decent shock from the 200v AC.... I do not remember getting any shock by touching the two ends of a lead acid battery from a car... It has a potential difference of 24v DC I think.
ok ok....Nigel is right, it depend, if you want to feel it, take out your shoes and touch it..., Lord loh is right too, current over 10 mili amps is dangerous thru your body, most over 30 miliamps is serius and can kill a person...I been working in wet locations and 12volts batteries make me feel that flavor in the mouth that some miliamps are finding the way to ground thru me...but under high humidity...over dry conditions, 40 volts dc, will not hurt you, try not to touch negative and positive at the same time....and trust me, dc is a way more dangerous than ac power...try your finger first, but the nail side , so if you get zap your muscle will retract and you get disconected automaticly....
Got to have a serious fault in the TV for that to happen, or the TV has been badly bodged (which I have seen!) - modern sets have isolated chassis's, but very old sets had live chassis's with isolated aerial sockets. The later 'very old sets' had modern highly safe aerial isolators, but really old ones just had a couple of capacitors, and bodgers often shorted them out if they failed - leaving the aerial fully live (depending which way round the mains plug was).
My boss, many years ago, was doing an aerial job in a garden - the pole was just stuck in the ground - so he got a tight hold and pulled it out. Unfortunately the TV had been badly bodged, and the aerial was connected directly to the live of the 240V mains - it threw him across the garden, and he broke his arm!.
I remember working on "live" mics on breadboard and it feeling ever so slightly odd at times. That was the 48vdc phantom power; its fairly safe to touch anyhow but I could feel it.
Yeah, my dad used the 'N' one a lot when I was a kid... He hated that I could take a useless piece of trash, and make it work without buying parts. Never understood it.
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