JT> Negative ion?

> Does it matter?

JT> I imagine it would give you more 'reach' into the room. That's
JT> why they specify pins (the sharp things that prick you in the
JT> middle of the night) as the output interface into the
JT> atmosphere. You are spewing out electrons after all.

 It's negative ions... but it's bullshit anyway.

JT> BTW, you get a little better performance if you leave out that
JT> limiting resistor- giving you a low impedance output to the
JT> surrounding air

 The capacitor is what gives the low impedance, and anything over
1000pF is plenty.

> I thought a standard resistor was rated at 250 AC. Oh! You mean
> the one at the HV end... it's better than nothing.

JT> The stupid thing is, that many AREN'T good enough for mains
JT> operation. Power supply filter bleed resistors are commonly
JT> garden variety, and fail on occasion. Using high voltage types
JT> improves reliability, and cost, so it might matter if you're
JT> doing a million of them. 

 Resistors connected to the mains are supposed to be "safety"
resistors defined in AS 3250 able to withstand 150% nominal voltage
and 10KV from 1000pF without changing value more than 50% (from
memory). In practice, any spiral-cut 1/2W resistor will pass.

JT> Now now, that bullshit speculation has yet to be proven wrong.
JT> Yet.

 According to the bullshit, they have to be *negative* ions (derived
from a negative high-voltage, not TV sets and monitors). No one has
ever proved that positive ions have a deleterious effect on hay fever
or asthma, or that negative ions fix it... or even that a little 5KV
spike has any affect on the charge in the air. If they were *serious*
about causing corona, they'd use a high-voltage pulse rather than
filtered 50Hz.

JT> Have you seen an effective improvement over a noral vacuum by
JT> using a dust monitor, or did you read the promotional blurb?

 I used to design vacuum cleaners. Pye was big is vacuum cleaners.

 The air coming out of the machine is fairly clean. Of course, it
also stirs up dust in the room, but so does walking or anything else..

JT> I read promotional blurb, (it's all bullshit). I wrote
JT> promotional blurb too, (it's also bullshit). It's written with
JT> the proviso that utlimately, the guy who's reading it, will
JT> want to actually buy it after reading it. 

 How did we move from engineering to PR?

JT> Can also be said that there is the same *airborne* dust levels
JT> after it's settled.

 You can say it, but it's not true. It *is* true that a standard
vacuum cleaner tends to remove the bigger particles while leaving the
small ones, but the HEPA filter and the Dyson cyclic filter get them
all. My experience goes back to the early 70s when Dyson was just
starting, and they called in the "brains" to see what the TV Lab 
could do with a standard vacuum cleaner. The answer was not much. It
surprised me that an ordinary paper bag worked so well.

JT> Although, the *important* thing is how much *airborne* dust
JT> exists after it's kicked around under *normal use* (walking
JT> around etc). Vacuuming removes a lot of it, but kicks up such a
JT> stink that makes it quite significantly worse (for about 2-4
JT> hours) than "normal" kickaround levels. 

 Yair... so vacuum once a week and get some benefit.

> HEPA filters rely on static. Dyson started the big change, now
> they're all doing it. They're still pretty useless...

JT> Static works as long as there is no significant airflow to blow
JT> it away from the attraction point. The back of your television
JT> works quite well.

 They make the airflow rotate in a vortex. In the old days, we just
used a powerful blower into a bag and let the bag do the filtering.

JT> You just have to remember to clean it out every so often.... A
JT> "vacuum cleaner' by it's very own purpose uses high air flow,
JT> defeating the purpose.

 So, use a bigger motor. Back in the 70s, a 600W motor was *big*. Now
the entry level is 1600w!

JT> Even if they do use a venturi (or whatever) effect to confine
JT> particles to a containment area. Works great for bits of paper
JT> in the demonstration, but pointless for stuff that you actually
JT> WANT to suck up. 

 Yes. We used to weigh the bag tested against an unmodified machine
on the same carpet. The head makes the biggest difference, and the
really hard part is to get it to work right to the edge.

Regards,
Bob
 

--- BQWK Alpha 0.5