Re: Capacitor safety questions

1) Voltage does't kill, current does.
2) You are just a large resistor.

The following is taken from
http://www.physics.udel.edu/~watson/scen103/colloq2000/safety.html
Note that the current has to pass thru the chest.
-------------------------------------------------------
Current effects on human body, current through chest
(A, amps)

<0.01 tingling or imperceptible
0.02 painful, cannot let go
0.03 breathing disturbed
0.07 breathing very difficult
0.10 death due to fibrillation

>0.20 no fibrillation, but severe burning, no breathing

-------------------------------------------------------

Dry skin has a resistance of 500K Ohms, so it would take 50,000V.

I set my multimeter to "mA", connected it to a 60VDC supply, then
washed my hands but didn't dry them. I grabbed my multimeter probes
in each hand and measured 1.2mA of current.

I then sprinkled table salt on my still wet hands and tried again.
The best I could get was 9.8mA and a barely perceptable tingling.

The internal resistance of a human body is about 500 Ohms. If your
skin were removed, it would then take about 50 volts to be lethal.

High voltages (115VAC, 230VAC) can kill by burning thru the skin at
the point of contact and then connecting to the much lower internal
body resistance. This takes time though, about 15 to 30 seconds at
230VAC. The heat generated is about 20W at the point of contact (200V
times 100mA) and takes that long to burn thru the skin.

The 9.8mA at 60V I tried generated a bit more than 1/2W (588mW) and
could do that; the body is simply too much of a heat-sink at that
power level.

As another reference said: "Electrocution is very difficult at
voltages below 100V, you must really work at it to succeed".

Safety suggestions:

1) Use only 1 hand when working with high voltages (115VAC or more).
Keep the other hand behind your back; never rest it on anything.

2) Don't stand barefoot on a concrete floor or don't stand on a wet
concrete floor with shoes on when working with high voltages.

3) When touching a high voltage, do it with the back of your hand or
back of your finger first. Should there be a shock, muscle
contraction will pull your hand away from instead of onto the
conductor.

4) Keep your hands dry. If they get sweaty, dry them often.

5) Obviously, have the power off. Off means the plug is pulled from
the wall. Always double check you see the pulled plug before you get
into the equipment if you walked away from it for even a minute.
Someone could have plugged it back in during your absence.


Mariss


--- In CAD_CAM_EDM_DRO@yahoogroups.com, "volitan712003"
<volitan@o...> wrote:

> Hello,
>
> I just ordered a 12,000uF x 100V capacitor for my power supply. I

know

> capacitors can be deadly but I have no concept of what a micro

farad

> is. If this cap is fully charged, is this thing big enough to kill?
>
> Another question is how can I check it so I know it's discharged.

I'm

> guessing it would have too much power to hook my volt meter up
> directly.
>
> Thanks!
> David