Kelly Averill Savino on tue 12 mar 02
(forwarding Bruce Girrell's post here - kelly)
> I am interested in building a waterfall type spray booth. However I would
> like to know if you feel that this kind of a spray booth is
> appropriate for
> weighing dry glaze materials? Will I risk getting my material
> wet?
The design of the booth should prevent any splashing from reaching the area
of application and the fan should be powerful enough to pull any residual
mist away from the application area. But I really don't know much about
waterfall spray booths - have seen them in action, never designed one.
> Also a question about magnets...
> My triple beam balance is the magnetized kind, I know that some fans also
> have magnets. I built a temporary spray booth and my scale does not
> cooperate very well. I could not get it far enough away from my fan and
> still stay on my table. Do spray booth fans typically have
> magnets? And if so how do you combat this problem?
Now magnets, that's something that I can talk about. Here's the short
answer:
It's unlikely that any magnetic field from your spray booth is affecting
your scale. More likely it is air motion.
As always, I'm happy to provide the long answer:
The magnets used in your triple beam balance are used to damp the motion of
the pan and beam. At the pointer end of the beam you will see a thin piece
of aluminum attached to the beam and housed in an enclosure. The enclosure
contains the magnets. The motion of the aluminum through the magnetic field
causes the generation of electrical currents in the aluminum (called eddy
currents) that also happen to generate a magnetic field that is in
opposition to the field of the magnets. This opposing magnetic field
provides a dampening effect on the motion of the balance and makes it settle
faster.
Although I suppose that it is possible, I have trouble imagining ways in
which the field from an electric motor could interfere with scale operation.
> And while I am on this subject, do electronic scales have magnets?
None that I'm aware of. And if they do, it's probably used with a Hall
element in close proximity, so there's very little chance of an external
field affecting it.
> I just got one of those for Christmas and haven't had a chance to try it
> out in the booth yet.
For heaven's sake, it's March. Unwrap that sucker and try it out. You'll
probably go back to the triple beam about as often as I abandon my
calculator to go back to my slide rule.
Bruce "magnetic personality" Girrell
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