On May 17, 8:03 am, "Arfa Daily" <arfa.da...@ntlworld.com> wrote:
Listen, friend. I don't have a problem with the validity of anything you
say
here, just the context. Of course the numbers are important *if* you want
to
do a statistical analysis of the waveform, or to start doing valid
comparisons between degrees of pseudo sine wave, and the real thing.

Review the first Arfa Daily post:
A 'modified sine wave' is not a three state square wave, although
you are on the right track. It is actually what you might describe
as a "poorly digitised" sine wave

IOW he looked on a scope, saw one output describes as a 'modified
sine wave', then assumed all 'modified sine waves' are same. Arfa
Daily failed to even grasp the 'whole wheat bread' example.

Modified sine wave can be most anything as long as there is a sine
wave inside that waveform. Even this UPS that is two 200 volts square
waves (no intermediate steps) is listed by specifications as a
'modified sine wave'.

So what is the output of that UPS? With only the phrase "modified
sine wave", then no one knows. As James Sweet noted, the problem is
not making a sine wave. The problem is amplifying it. Using filters
to convert a square wave into a sine wave (at that frequency and
amperage) would be even more expensive. That cost also should have
been obvious to that poster.

Since computers are so robust, then most UPSes simply output
'dirtiest' electricity when in battery backup mode. Dirtier means it
may even harm small electric motors. Without numerical specs from the
UPS - such as THD - then no one can answer with certainty. Worse is
the quoted post from Arfa Daily that is misleading. Then is followed
by his emotional outburst - and no numbers.

Power on surge current from a laser printer is only one of many
reasons why UPS manufacturers quietly recommend no laser printers and
no power strip protectors on their output. This UPS that claims to be
a 'modified sine wave' is two 200 volt square waves (no intermediate
step) with a spike of up to 270 volts between those square waves.
This 'modified sine wave' would probably create noise and heating as
described by James Sweet's large transformer experiment. It may also
be harmful to some small electric motors. It is called a computer
grade power UPS because it is intended for devices far more robust -
such as computers.

'Modified sine wave' is a subjective description for color glossies
- for the technically naive. The phrase provides little useful
information. Answers based in reality start with numbers from
manufacturer's specifications.

What UPS outputs sine waves sufficient to power a laser printer?
How many $thousands did it cost?

You can slag me off all you like - although I would point out that I was

that's all I'm saying, and that you seem to be going to a great deal of
effort to completely miss this point.