From: Dmerrill@bnr.ca (Dana Merrill)
Subject: Re: Does grounding the sump work?
Followup-To: rec.aquaria
Organization: BNR
Date: Thu, 10 Sep 1992 13:26:36 GMT

In article <1992Sep9.230658.15097@cs.ucla.edu>, jason@lanai.cs.ucla.edu
(Jason Rosenberg) wrote:
> 
> sh240031@wvnvms.wvnet.edu writes:
> 
> >Ok. Let me try this again.  I disconnected the wire from the screw.  I attached
> >on end of the volt meter to the disconnected wire and the other end to the
> >ground screw.  This effectively measures the voltage from the tank, into the
> >electrode, through the meter(~70 VAC) into the ground screw.
> >
> 
> Carl,
> 
> It sounds like your confusing the measuring of current with voltage.  Voltage
> is not something that flows or travels.  It is a potential energy level.
> A voltmeter effectively does not allow any current to flow (well, very
> miniscule amounts).  You have connected your voltmeter in series, which
> is really how you would want to connect an ammeter to measure current flow.
> To measure voltage, you need to connect your voltmeter in parallel.  That is,
> leave your grounding circuit intact, and measure the difference in voltage
> potential at the electrode and the ground screw, while not disrupting the
> normal operation of your circuit.  So far, you have only measured the voltage
> that exists in your tank when there is no grounding (since you effectively
> disconnected your grounding circuit to insert your voltmeter).  So, 70vac seems
> about right for a typical induced voltage (not grounded).  If your circuit
> is properly grounded, you should measure close to 0 volts.
> 
> So, we are still waiting to hear the results of your next experiment to
> find out if grounding the sump is ok.......
> 
> Jason
> 
> -- 
> Jason Rosenberg                           Computer Science Department
> jason@cs.ucla.edu                         University of California
> {uunet,rutgers,ucbvax}!ucla-cs!jason      Los Angeles, CA  90024

Seem to be making a mountain out of a mole hill to me folks!

Measure the potential (Yes the volts scale) with one probe in the
tank and one on the ground screw.  If it reads Ov AC then then the
ground in the sump is effective.  (Take it out and repeat the 
measurement and the 70 VAC should return).

By the way, sounds like a big rip off to me.  Big bucks for a piece of 
wire with an electrode? (Am I missing something here? I'm not familar
with the grounding product that was described.)

There will be virtually no current in such a grounding circuit and 
therefore any wire connected between the ground screw and the tank 
water should do the job.  Only concern that I see is the conductor
(metal) that is in contact with the water must be considered.
Obviously don't want copper in the water so what about aluminum?
Would that be harmful? If not, use an aluminum wire. If that is not
OK, some conductor could be used for an electrode on the end of
the wire.  What about stainless steel?  Maybe someone else has an idea
for the electrode.

==================================================================

Dana Merrill                                Bell Northern Research
DMerrill@BNR.CA                         Research Triangle Park, NC
==================================================================