[time-nuts] Improving the stability of crystal oscillators

Bruce Griffiths bruce.griffiths at xtra.co.nz
Mon Oct 15 22:54:48 EDT 2007

Don Collie wrote:
> Hi Hal,
>     I was thinking of attaching a temparature sensor [AKA Star Treck] to the 
> cold side of a Peltier [what`s the other type? Are they available/better?] 
> pile. and driving the pile from the output of some sort of servo loop to 
> maintain a temparature of ,say , 0 Degree C.
>      If you wanted a double oven, you could heatsink a small oven, 
> containing the crystal, the oscillator, and buffer[s] to this, and use a 
> second servo loop to raise the temparature of this to 25 Degrees C working 
> against the Peltier. In this way, you could maintain the crystal, and 
> circuitry at 25 Deg C., over an ambient temparature of 0 to ,say 70 Deg C.
>     Yes, you can cut a crystal to have an inversion temp at 25Deg C. [well 
> certainly with an AT cut - I`m not sure about the SC cut.]
> Cheers,............................................Don C.
> ----- Original Message ----- 

With such a wide swing in the temperature differeence across the Peltier
stack, you will need to adjust the PID loop parameters to maintain
optimum control.
A fixed set of parameters is only useful for a temperature range of up
to 10C. The Peltier stack performance varies significantly with the
temperature difference across the stack.
Consequently you also need to sense the peltier device heatsink temperature.


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