On 6/24/2012 2:45 PM, Jim Wilkins wrote:
wrote in message
...
On 6/24/2012 11:35 AM, Jim Wilkins wrote:
...I monitored the 240V line current with a clamp-on current probe
jsw

I did exactly the same thing to log my water heater consumption.
That works fine for devices with power factor of 1, like a water
heater.
It can give you a hint about relative consumption, but the actual
power you compute from RMS current * RMS voltage = VA is not real
power (watts) if
your power factor isn't 1. Many devices are .6 or so. Computers,
CFL,
anything with a motor, most electronic stuff. And even your current
number isn't right unless you use a real RMS responding clamp-on
meter.
Most aren't.

You must be new here. R.C.M. is the land of homebrew 3-phase rotary
converters with carefully balanced leg currents. Alt.energy.homepower
is where power factor has to be tediously explained, over and over.


That brings up a topic near and dear to my heart...Communication.
What is the appropriate level of response when you think you can
correct a misconception?

It's been my experience that much of the discourse, not to be confused
with communication, in the newsgroups is based on serious misconception.

The ratio, signal divided by noise, in the newsgroups approaches zero.
And the previous sentence is a symptom. I started with "signal to noise
ratio",
but immediately recognized that some net cop was gonna argue with the
definition and start a flame war.

When people ask a question, I try to put myself in their shoes,
try to figure out what they really want to know and construct an answer
in a context I think is relevant to their task and that they might
comprehend. That's hard to do in
a half-duplex mode like newsgroups. There's lots of opportunity
for the thread to get sidetracked during the response delay time.
I try to be tactful, but making the point requires some directness.
And the "experts" start piling on before the question is even clarified.

Sometimes, the guy on the other end has a misconception. Or maybe
he just abbreviated the situation. Or maybe it's a typo. Or maybe I
misinterpreted. Or any number of other things.

When somebody sez, "I monitored the 240V line current with a clamp-on
current probe", what's a rational assumption? Since most people don't
understand power factor, and most clamp-on current probes plugged
into DMM's don't have
any means of phase output even if the DMM does have a serial port, and
you need phase info
to calculate power, should someone respond with a short discourse on
power factor?
It's not just an argument over a term, it's a major error factor.

It matters not that everything you ever need to know has been discussed
over and over somewhere else. The only thing that matters is whether the
OP, or the lurkers, might benefit from a short discourse.

So, if you think you can POLITELY help, should you?