[filmscanners] RE: Power Line Filter

["Austin Franklin" <darkroom@ix.netcom.com>]

> 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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