Re: Voltage NOT problem, CURRENT is!
Some cutting of the original post to save bytes.
>How to test for stray voltages: Grip one prong of one of those little neon
>circuit testers in your hand, touch the other prong to the cover glass, then
>to the water itself. The light will glow brightly at a current flow too
>small for you to feel it. A really bad voltage leak will usually light the
>neon bulb just by touching the cover glass. (Bet you didn't know that there
>is almost always a very thin film of water on that cover, connecting with the
>water in the tank?)
First, I'd like to say that I liked the idea of using one of those little neon
circuit testers to test for bad voltage leaks. I guess when using this device
by gripping on end of the prong that the neon circuit tester will limit the
current through your body to a safe amount?
>Now, why do I not believe in those neat little expensive grounding
>electrodes? Well, they just provide a path from the current to the ground.
> If the leakage is from the other end of the tank, everything in the tank
>between the electrode and the leakage source is getting shocked. Tell me,
>what did you gain? Remember, the voltage is a pressure thing, and it is not
>just an evil being, wandering around the tank aimlessly, looking for things
>to shock!! The flow of electricity, the current, will always take the lowest
>resistance path to the ground, or to the neutral wire. Frankly, I think
>grounding electrodes are a lot like those water softening magnets.
I thought the main purpose of these grounding probes is to shield the fish from any stray
induced currents caused by turning on fluorescent lights, or other near by electrical
applicances. One can see the difference in how much the fish jump when turning some
lights (fluorescent lamps in particular) with or without these probes. One may debate
if there really necessary to have these probes, but for me, it was easy do-it-yourself
project that cost about five dollars. It gave me something to do. IMHO, even the
$15-$20 cost of the commercial units are cheap compared to the cost of all the equipment
one gets for an planted aquarium.
I haven't seen anyone claim that these devices will protect you from a potentially
lethal short circuit in the aquarium. IMHO, I'd say that the ground probe may help
in that the probe gives an alternative (with relatively low resistance ) current path
to ground rather than having all of the current going through your body. Most powertools
are grounded for the same reason. In either case, I would _not_ bet my life on a grounded
aquarium or a grounded powertool. I like the *.aquaria FAQ's idea of turning off all
aquarium electrical equipment (heaters, powerheads, filters, lights, etc...)
before sticking your hand in the water.
Perhaps the biggest statement in this post I take issue with is the title
"Voltage NOT problem, CURRENT is!"
in that it may mislead people into thinking voltage is a nonissue.
Its really the combination of all three variables that are important. (Voltage,
current, and resistance are all related through Ohms law.) From a point on view
of not getting shocked, one doesn't want to become a low resistance path to ground.
(i.e. Don't stick your hand into a operating aquarium while standing with bare feet
on a wet grounded metal plate.) As far as voltage is concerned, I'd rather not stick
my hand in a shorted aquarium with either 24 volts connect to a "good" supply or to
a short connected 110 Volt house supply. But given the choice, one would have a
significantly better chance of not getting hurt from a accident involving a 24 Volt
transformer supply than from a 110 Volt household power supply. And the third way to
reduce the chance of getting shocked is to use fuses and Ground Fault Interrupt devices
to limit the current (also recommended in the *.aquaria FAQ.)
I guess what the title is trying to say is that a shock from rubbing your feet on
dry carpeting and touching a door knob (high voltage with low current) is not
the same as being burnt by an arc welder (low voltage with high current.)
Ron Wozniak Allentown PA, USA
rjwozniak at lucent_com