RE: E-meter amps help (how did it live?)

["Roger Stockton" <rstockton@delta-q.com>]

OK, so you removed the ground reference so that the E-Meter ground was
largely free to float wherever it wanted relative to the pack.  The
prescaler tied to pack positive would have kept it from floating *too*
far (i.e. from about 0.7V above pack +ve to about 372V below pack -ve).

The shunt was still tied to pack negative, and, since they were
effectively shorted together by the shunt, the wonky reading you saw had
to be the result of the E-Meter ground floating sufficiently that the
current sense inputs went out of range.  I think Lee has said they will
take about 5V of common-mode voltage, so perhaps your ground floated far
enough from pack ground to get wonky readings, but not far enough to
permanently fry anything.

Cheers,

Roger.

> -----Original Message-----
> From: owner-ev@listproc.sjsu.edu 
> [mailto:owner-ev@listproc.sjsu.edu] On Behalf Of Paul G
> Sent: November 29, 2001 5:31 PM
> To: ev@listproc.sjsu.edu
> Subject: RE: E-meter amps help (how did it live?)

[snip]

> The e-meter runs off the accesory battery, through a DC>DC. 
> That negative connects to the same point as the prescaled 
> pack negative, at the e-meter. So the e-meter was powered and 
> displaying still. I agree with the logic of the statement 
> above, but it didn't match what I actually saw. And so I 
> started wondering (while thanking my wife for catching it, 
> and thanking the e-meter for surviving).
> 
> Neon
>