Re: Line Noise Interference Question

["Robert Green" <ROBERT_GREEN1963@xxxxxxxxx>]

"Dave Houston" <nobody@xxxxxxxxxxxx> wrote in message

> Without knowing exactly what components are used in each filter, it's hard
> to say what interactions are possible.
>
> Ground loops might cause erroneous results.

I've been reading here:

http://www.copper.org/applications/electrical/pq/issues.html

Where they say:

"As we apply a voltage to a solid state power supply, the current drawn is
(approximately) zero until a critical ?firing voltage? is reached on the
sinewave. At this firing voltage, the transistor (or other device) gates or
allows current to be conducted. This current typically increases over time
until the peak of the sinewave and decreases until the critical firing
voltage is reached on the ?downward side? of the sinewave. The device then
shuts off and current goes to zero. The same thing occurs on the negative
side of the sinewave with a second negative pulse of current being drawn.
The current drawn then is a series of positive and negative pulses, and not
the sinewave drawn by linear systems. Some systems have different shaped
waveforms such as square waves. These types of systems are often called
non-linear systems. The power supplies which draw this type of current are
called switched mode power supplies. Once these pulse currents are formed,
we have a difficult time analyzing their effect. Power engineers are taught
to analyze the effects of sinewaves on power systems. Analyzing the effects
of these pulses is much more difficult."

Does the chopping of current near the zero crossing of switching power
supplies affect X-10 or is it the filtering of such choppiness in the power
supplies themselves that causes the problem?  I have a lot of switching
power supplies that cause problems, but a also a few that don't.  I'd like
to know what differentiates the two.

--
Bobby G.