[Lowfer] HiFER freq stability

[Bill Ashlock]

>I am not an expert thermodynamicist, but it seems to me you would still get
>a "sine wave" temperature plot without a stable heating or cooling source,
>though it will be slower than without the foam.

Kurt: You will always see a sine-like temperature characteristic with any 
contol loop when there is a time delay involved, BUT the secret is to design 
the contol loop so that the amplitude of the sine is acceptable to the 
application. So you need to first determine what temperature fuctuation is 
accepable for YOUR oscillator. The heating source will usually need to be 
proportionally contolled (OP amp typically), but not always.

There should be a circuit available in some publication that will work. Were 
talking only about 6 components here (thermister, OP amp, and 4 resistors).

Bill A



>----- Original Message -----
>From: Eric Smith <eric@willow.nutstreet.net>
>
>Hmmm...very crude.  Only a styrofoam cap over the oscillator, cut from a
>cooler, and weighted down tight over the chip, and lots of insulation
>around the whole circuit.
>
>
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