CDU voltage

"Bob Heath" wrote

I don't know the answer but I'm sure if you email Gaugemaster they will give you an indication of the voltage theirs put out.

The input votage will possibly also have an influence. I know some people who run them on 24v.

John.

I will give that a try Bob

The voltage won't be any higher than the voltage accros the capacitors when fully charged; probably around 16VDC but will depend on the supply voltage. However the current during discharge is considerable, definately painful and possibly fatal. If you think you have crossed wiring I recommend that you disconnect the CDU and do continuity checks (low resistance/low value of ohms) between the CDU output and where you think the wire goes.

capacitors

I think you need electric shock therapy!

You would have to try *really* hard to get a fatal shock from a 16V CDU. The current during discharge is only high due to the low resistance of a solenoid point motor. The resistance of dry skin is orders of magnitude greater, hence the current will be tiny.

MBQ

once more with feeling....

painful on the tongue, deadly with an open chest applied straight across the heart... other wise.. no. Not either of the above

We've all seen these statistics that say "last year three people died from testing a nine volt battery on their tongue"... no. lies. not possible - not unless the surprise made them back of a cliff or similar... in which case the batterys culpability is questionable.

haing nothing better to do, I have just measured the resistance of an inch of mistened finger... and the lowest I could get (even pressing painfully) was 2.3Mohms Ohms law states (correctly) V=I*R thus I=V/R = 16/2,300,000 = current of 6.9 millionths of an amp. You wouldn't feel that on your finger and the current is bearly sufficient to induce neural response...

states that in TENS machines (pain relief thru electric stimulation of nerves) Currents *start* at three thousand times higher than this. A bearly perceptable 20mA and go up to

120mA (1/8 of an amp) which would undoubtedly be painful.

But much lower resistance if hot and sweaty, especially when soaked in salty water. It only mA's of current to kill you.

Chris

Soaking oneself in salty water isn't a common pastime I hope ;-)

16V applied across a human body, ie hand to hand so it passes through the chest, cannot cause enough current to flow to cause fibrillation of the heart in a normal person. If it could, it would not be classified as a 'safe' voltage. If you are hot and sweaty, some of the current is diverted through the sweat over the surface of the skin anyway, rather than through the body.

It takes around 100mA to produce vetricular fibrillation, though lower currents are still hazardous. 16V isn't going to cause 100mA to flow through a human being.

10mA can produce muscle spasms local to the shock, which could result in injury, but the shock itself would not be directly dangerous- just unpleasant. 16V is highly unlikely, even in ideal conditions, to cause even 10mA to flow across a human body hand to hand.

Motors and solenoids have inductance and even small ones generate a high enough back EMF to give a harmless jolt under the right circumstances, but the 16V supply is perfectly safe. If it wasn't, I'd have died years ago as I regularly work with both low and high voltages.

Dave

The point I was making is that current is what kills not voltage and that skin resistance does vary between people . I knew one chap who had quite leathery skin who could put his hands across a 650V bus bar with no effect but for others it would be fatal. You are right that 16v is unlikely to breakdown resistance and that is why 110v is the voltage specified for industrial tools working outside.

Chris

Be careful what you say, since thet *doesn't* mean that 110v can be considered safe.

Industrial tools are run from grounded centre tapped transformers so that the "live" wires are never more than +/-55v from ground. That *is* considered a safe voltage. You might still come to harm if you grasped both live wires in either hand but you would most likely survive the more common live to ground conection via your body.

MBQ

In message , Dave D writes

Doesn't America's Electric chair for murdering people have 2000v from head to foot with both covered in salt water? People have been known to survive that. I expect that at some time or other most of us will have touched both terminals of a fully charged car battery and not felt a thing.

I didn't say that it was safe but as likely to breakdown skin resistance as 220/240 EU mains voltage. However the US 110 mains runs at 60Hz which is a frequency that can interfere with the heart, not explaining it well but a different effect than having current through the body.