Dan Michaels wrote:
> Mark  wrote:
> ....
> >>
> >> Plus, I suspect you could use 2 or more thermistors arranged
> >> vertically within the tube, plus a little math, to actually
> >> determine the level, not just whether above/below one point.
> >
> >True on multiple height determination - though (despite my being pretty
> >good in math) I don't see where the math's needed/applicable.  I thought
> >with 3 hot beads, you'd know one of 4 states, {"Height < A" || "Height
> >>= A" || "Height >= B" || "Height >= C"}, don't see how you can determine
> shades of height between say A and B (putting A lowest, C highest here, to
> clarify.)  Am I missing something?  Has been a "Bad Brain Day" to some
> degree <G>  (There's not a big difference for thermistor B in temperature,
> between temperature for water say 1 foot below it and 1 inch below it,
> barring splashing, is there?  Has been a while since I last hot-beaded <G>)
> >
>
> Not that I've ever tried this, but I figure the temperature variation
> would distribute itself along the tube in some manner [to be measured
> and calibrated empirically], and the math would be some weighted
> averaging routine. Just a thought. The sorta thing you try once, and
> immediately get a strong hunch whether it will ever work or not.
>
> - Dan

Aaah, you're thermally bonding the hot beads to the tube?  Perhaps
that'd work, might want to instead put a heater at the top of a small
rod, bond the thermistors to the rod, use them to measure along the rod,
maybe would work.

Good news is that you can use one larger PIC and run quite a few
thermistors simultaneously to get many data points simultaneously.
Sigma Delta code's not too hard to find <G>

  Mark