Isolation transformer source

On Sun, 13 Jun 2010 23:16:44 +0100, "Dave Plowman (News)"
<dave@davenoise.co.uk> wrote:

In article <as-dnYa6P-Qth4nRnZ2dnUVZ_tSdnZ2d@earthlink.com>,
Michael A. Terrell <mike.terrell@earthlink.net> wrote:
If using a proper isolating transformer, there will be no reference to
ground even with a 'live' chassis. The only way to get an electrical shock
is to touch both outputs from the transformer.


Not true. You connect the chassis of the UUT to the test equipment,
so ANY voltage you contact inside the UUT is referenced to ground.

Why is the test equipment grounded?
Perhaps you are a little inexperienced. There was a time when

virtually ALL test equipment came with a two wire (ungrounded) cord.
Then it was decided that having technicians electrocute themselves was
undesirable from both efficiency and moral viewpoints. As a result,
signal generators, oscilloscopes, frequency counters, alignment
generators, etc all were supplied with a 3-wire cord. Thus, when an
oscilloscope was hooked to a live chassis TV the probe ground burst
into flames rather than the technician falling to the floor in cardiac
arrest. Of course, there were those brave (or foolish) souls who cut
off the ground pin on the power cord to save a few dollars. While
others might disagree, I feel that using an isolation transformer is
preferable to losing my life.

PlainBill

 

[JW]

On Mon, 14 Jun 2010 09:58:33 -0500 Chuck <ch@deja.net> wrote in Message
id: <ajgc16p7cqki5n2m5hntcdg2gd2okvgn44@4ax.com>:

On Sat, 12 Jun 2010 07:01:32 -0400, JW <none@dev.null> wrote:

On Fri, 11 Jun 2010 08:24:36 -0500 Chuck <ch@deja.net> wrote in Message
id: <r7e416tt40mloqh91evegbjo9eb2qllqjk@4ax.com>:

On Thu, 10 Jun 2010 09:44:12 -0400, JW <none@dev.null> wrote:

Can anyone recommend a good isolation transformer for sale on-line?
Need one that will handle 5 amps or so at 120VAC, and have a standard AC
plug at the outlet. Prefer one for less than $100 or so, unless that seems
unreasonable. Found one at Mouser for $114 but that's only good for 1.25A.
Getting lots of irrelevant hits on google...

Thanks.


MCM Electronics has one. Chuck

Thanks Chuck. Looking at these for the moment:
http://www.mcmelectronics.com/product/TRIPP-LITE--POWER-PROTECTION--IS500-/28-10160
http://www.mcmelectronics.com/product/TENMA-72-1097-/72-1097

A bit more than I wanted to spend and a little less current capability,
but those may be the breaks.

Check out stock number 72-6670 isolation transformer $65.00. We've
had one for years and it works very well. Chuck

Looks like we have a winner.

Thanks again, Chuck. And thanks to all who contributed to the thread.