chuck wrote:

Some observations:

Be extremely careful in measuring the
voltage across a galvanic isolator. If
the isolator should be "open", there may
be a dangerous (possibly fatal) shock
hazard between the two isolator
terminals. This is all the more critical
since you usually suspect an electrical
problem when you have to resort to
checking your isolator.

Before setting the DMM to DC, set it on a higher (start at 200V) AC
setting and measure across the isolator. If it reads zero, switch it
lower until you can see a 2V AC reading. If you see a high AC voltage,
the isolator is open AND you have a dangerous fault onboard. If it reads
a couple of volts AC, the isolator is OK, but you still have a fault (or
leakage). If it reads an AC voltage no higher than the diode drop,
you're OK. The switch to DC and check for galvanic currents.

A DC voltage reading across the isolator
of zero or near-zero volts is a highly
desirable situation! It means that
galvanic (and other DC) currents passing
through the shore power ground system
are negligible, and that is always
desirable. A reading of zero volts does
not automatically mean the isolator
diodes are shorted!

Similarly for AC voltage readings of
zero or near-zero volts. A reading of
zero volts AC means there is no evidence
of appliance leakage on your boat and no
reason to suspect problems with AC
wiring on neighboring boats.

Its always a good practice to check the AC voltage of anything first.

Chuck

----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption =----

--
Paul Hovnanian
------------------------------------------------------------------
Marching to a different kettle of fish.