[GPS_Standard] RE: Xtal Oven coming up to temperature from cold?

[Zack Widup]

On Mon, 18 Dec 2006, Dick wrote:

>  
> Nice to see you on the 'List' Zack and thanks again for originally pointing
> me in this direction <grin> ... I have ordered some of the IC's (another day
> or two to get here) but in the meantime I'm building up the various 
> supporting' circuitry !! 
>  
> To manually do things is, for me anyway, a no-no !! .. I like to automate
> things (guess I'm basically lazy <smile>)  - I run a ham-radio BBS on radio
> and Internet - I have written small programs/scripts for Linux to do many
> chores which I originally did manually .. So the die is set - I like to
> automate - I get a real big kick doing it that way <smile> .. 
>  
> With regard my Pin-1 reset pin on the PIC, I have decided that I can take
> advantage of my 24 volts starting off at 18 volts with a cold oven and
> approaching 24 volts when the oven has stabilised .. 
>  

I thought about that.  The HP 10811 series oscillators have an oven 
temperature monitoring pin.  From the HP manual for this OCXO, it appears 
the output voltage on this pin starts out close to the oven supply voltage 
when it's cold and drops to around 3.5 volts when it reaches operating 
temperature. For the Isotemp OCXO's I have, the oven temperature 
monitoring pin starts out at 0 V when cold and comes up to 0.7 volts when 
operating temperature is reached.  In any case, it would be a simple 
matter of making a circuit that held the reset pin on the controller low 
until the oven monitor pin changed output value.

73, Zack W9SZ