Ground Loop Isolators

[Paul Schreiber]

NO NO NO!!

What you are referring to is called an isolation transformer. It "floats" equipment from earth ground. The 2 most common uses are to float oscilloscopes for measuring telephone line signals and to measure the primary side signals of switching power supplies (which I learned the hard way is -375VDC referenced to earth ground!).

A good selection of isolation transformers are in the Allied and Newark catalogs. I use an IsoBar model ISO-800, which is in a nice enclosed case with power switch/light and multiple outputs. 

Prices are based on the VA (volts x Amps = watts [not adjusted for power-factor, but let's not down that road!]). So if your scope draws 3 amps off 110VAC, you would get a 500 VA unit. Most synths are quite low powered, so a 200VA would be fine.

Roughly, they cost around $0.25 per VA.

Paul Schreiber
Synthesis Technology

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From: 	Rob01[SMTP:cyborg0 at midwest.net]
Sent: 	Thursday, April 03, 1997 3:49 PM
To: 	03sjbrown at bsuvc.bsu.edu; synth-diy at horus.sara.nl
Subject: 	Re: Ground Loop Isolators

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> From: 03sjbrown at bsuvc.bsu.edu
> To: synth-diy at horus.sara.nl
> Subject: Ground Loop Isolators
> Date: Wednesday, April 02, 1997 7:48 PM
> 
> 
> 
> I understand what ground loop isolators do but exactly how do
> they work?
> 
> And my biggy question --> are all ground loop isolators created equal
>                           or are some a bunch of crap?
> 
> 
>                                                 Shawn Brown
Weeell, 
to tell you the truth, sometimes all thats needed is to use 3prong to
2prong adapter.
on some of the AM circuits i breadboarded, we had to isolate the
Oscilloscope from 
the power ground to get a good signal...You could always try that..
                  Rob01
             Zeros & Ones
The Mind Controls the Machine 
The Machine Controls the Body