On Mon, Nov 15, 2010 at 12:54:51PM -0800, Lew Hodgett wrote:
> "Ben Okopnik" wrote:
>
> > Lew, that's an interesting statement. What's unreliable about a
> > well-designed float (e.g., http://x.co/KGoQ), or for that matter,
> > the
> > cycling pump that we were talking about?
> -------------------------------------
> Everything.
Really? The plastic evaporates and the stainless screws explode, I take
it? :)
> Float switches define the baseline of a failed application.
That's a pretty categorical opinion - and one that's incorrect without
some serious qualifiers. I agree that the standard float switch isn't
worth spit, but that's not all there is. I can certainly think of one
that'll survive anything a boat bilge can throw at it that can be built
for under $100; the fact that people don't want to spend that kind of
money (plus profit/shipping/etc.) on a float switch doesn't mean float
switches are bad as a category.
> I make a living replacing failed float switches in the industrial
> market.
Did you look at the one that I mentioned above? It's what the Coast
Guard uses. Gunk wouldn't bother it.
A friend of mine is a process engineer in the petrochemical industry,
and I've seen the float switches they use (a design somewhat similar to
the one above, but much larger and with more space around it). You'd
starve to death if you tried to make a living replacing those. :) If one
of them ever fails, it'll be because somebody dropped bombs on that
refining plant.
> Continuous ultrasonic suffers from gunk build up and/or foam, same
> with ultrasonic point level (gap switch) technology.
Perhaps we're thinking of different configurations. The one I've seen
simply bounced a beam off the surface - no chance for gunk to build up
on it, since it was never within reach in the first place.
> Bottom line, of the 10-12 level measuring technologies available, none
> can provide a reliable solution at a price, physical size, and power
> consumption the market can support.
This is a more reasonable position, but perhaps still incorrect. There
is no "the market"; there's a range of markets. I'd be willing to bet
that most people on this list would spend $100 for a no-fail bilge
switch - but the average recreational boater would not. Long-distance
sailors would; occasional weekenders, probably not.
The demand may be too low to assure a supply that's commonly available -
but the good-quality solutions are definitely there.
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