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Old 10th May 2011, 12:39 pm   #14
kalee20
Dekatron
 
Join Date: Feb 2007
Location: Lynton, N. Devon, UK.
Posts: 7,061
Default Re: Beware!

The trouble is, if you put a resistor in series you clobber the effectiveness at higher frequencies.

As a spark suppressor, a resistor in series to form an RC snubber is used (indeed, is often necessary). But as an RFI filter, you want as low an impedance across-the-lines as possible.

An added complication is, if the capacitor fails but the little series resistor blows open as intended, the user would probably never know but the equipment would have lost its filtering. If the equipment is a noise source, and the filter was to stop the interference getting out, it would be anti-social to say the least.
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