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Stray voltage and grounding probes

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---------- Forwarded message ----------
From: "Davy Cleys" <davy.cleys at skynet_be>
To: <Aquatic-Plants at actwin_com>
Subject: HELP! Stray voltage and grounding probes
Date: Mon, 8 Oct 2001 21:58:06 +0200

Hello all,
I have a fully automated CO2 system in my new tank with a very sensitive
pH-sensor (accuracy 0.01).

Whenever the fluorescents light come on, I am not longer able to get a
stable pH-reading from the sensor. The readings go back and forth between pH
6.80 and 6.85 while switching CO2 supply on and off almost continuously
(switch hysteresis is 0.05). I attribute the cause for this to stray
voltages induced by the lighting (hood or fluorescent tubes?). My neighbour
electrician says that it must come from the tubes since the hood has an
electronic ballast with capacitors... (whatever that may be...)

When I put a copper electricity wire into my tank and connect it to the
grounding eyelet of my electricity socket, the pH-readings become very
stable again, only changing very slowly as CO2 escapes back into the air
(the tank has no plants or fish yet). Of course the copper wire can only be
a very temporary solution since it is probably / definately leaking copper
into the water...

So my question is where I can find a good quality grounding probe that does
not leak any heavy metals into the water and that can resist corrosion and,
above all, which is safe to use (e.g. no water leaking into electricity
socket via wire insulation). Does anyone know of a (possibly European)
source of good grounding probes?

Any suggestions?

Davy Cleys