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Re: Ac in tank

Date: Wed, 22 Apr 98 02:37:50 -0400
From: RicCooney <RicCooney at Worldnet_att.net>

>I just got a great instrument from Hanna Instruments. Its called the pH 
>turtle. It connects a  PC computer running windows 3.1.1 or 95 etc to a 
>pH probe, and allows you to graph the output  at various times into a log 
>or graph.

I'm thinking this pH turtle is not as great as you think it is. 

>Now the problem. My Fluval 403 and my Computherm heaters are inducing ~ 
>0.01 ma apiece so I can't leave them on otherwise the meter goes crazy. 

Never had a problem with our 4 pH controllers being bothered by other equipment. 
Besides heaters and powerheads, FL lights will induce voltage into the tank.

>If I ground the tank water, apart from creating a potential problem for 
>the fish, I peg the probe at 14.0 pH.

All our tanks have grounding probes to reduce the risk of diseases such as hole 
in the head and fin rot and the pH controllers still work perfectly. 

>So....What do you guys with the pH controllers do? Help George and any 
>other EE's out there.

A pH monitor is a VERY sensitive circuit. I wonder if the design is correct and 
robust enough? I wonder if there are ground loop problems involved (improper 
isolation of the PC power supply and the probe circuitry)?