[filmscanners] Re: Power Line Filter

["Owen P. Evans" <opevans@ca.inter.net>]

Well I stand corrected! The theory is substantive and as I said in a
previous post; enough science will convince anyone of anything. Whether or
not your science is real or pseudo, I don't buy into it. I shall agree to
disagree and stop bothering you with my opinions. By the way, I mistakenly
wrote graphite rings & beads; now I wonder if they were ferrite rings &
beads? Who cares they don't work for you and they didn't work on my RFI
loaded home in the city anyway.
Good scanning to everyone and may the Force be with or without you depending
on how much your scanner can stand!

Cheers,
Owen

----- Original Message -----
From: "Austin Franklin" <darkroom@ix.netcom.com>
To: <opevans@ca.inter.net>
Sent: Saturday, March 30, 2002 10:31 AM
Subject: [filmscanners] RE: Power Line Filter



> EMI interference should be taken care of by the engineer who builds the
> power supply.

It SHOULD be, but isn't always.

> If RFI
> interference is present then graphite beads or rings around the power cord
> will eliminate this.

Not necessarily.  We have had to use quite elaborate filters (ala Corcom) to
eliminate EMI (which is called conducted when talking about cords).

> All in all the voltages being amplified in a scanner are nothing
> like audio
> preamp requirements.

Well, that's not true.  Both use 14 to 16 bit converters (scanners use A/Ds,
and CDs use D/As), depending on your scanner.  The voltage swing is the
same, typically +- 3V...so if both us 16 bit converters, and have the same
voltage swing...they are equally as sensitive...and that doesn't take into
account the CCD sensitivity...and analog front end gain, and the stepper
motor (which could generate a LOT more EMI, because of the pulsed nature of
a stepper).

Austin

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