I'm looking for an easy-to-control water tank heater.

The idea is that the 5 USGal (19L) tank goes in the
freezer, where it is cooled to 1 deg C, or less, and
then the heater starts to do its thing, bringing it up
by about 1 deg C at a time until it reaches room
temp, at which point we'll take it out of the freezer
and go up from there to about 50 deg C.

It should loiter at each step until the temp has been
stable (say, less than .05-.1 deg C variation) for
about 1 hour.  After that hour, it should go up a
degree then stop.

Ideas for making are okay, but ideas for buying are
even better.  I can't seem to find any products that
do this.  Price is an object, but $200-$400 isn't at
all out of the question.

Mike H.

PS- Here are my "ideas for making":
We have a heater already which is controlled by
10-turn pots.  I could (maybe) replace the pots
with a digital pot, and use a PIC with a thermistor
to determine temp stability.
Use conventional "lamp dimming PIC" methods
to vary the strength of an aquarium heater.
???

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