[time-nuts] E1938A source code/ firmware

[Glen English VK1XX]

Hi Rick

Thank you very much for the reply and the suggested leads. I think your 
work on the balanced bridge oscillator was both preeminant and seminal .

I have read all the papers on it, and there are few other things in my 
30 years of this field professionally that really impress me as much  in 
the new approaches and new thinking on the entire unit. Agreed on the 
PII^2D control system.

I've built a few OCXOs back in the 90s, the best I did on (inner) oven 
control was using dual glass bead thermistors in a bridge configuration 
with lots of gain driving a simple opamp integrator. The opamp was 
chopper stabilized and I ensured the op amp never operated in the 
crossover region of the opamp output driver.  These were on AT cuts  at 
97 deg C ...

cheers

Glen. AI6UM  / VK1XX



On 6/07/2019 2:37 PM, Richard (Rick) Karlquist wrote:
> On 7/5/2019 8:20 PM, Glen English VK1XX wrote:
>> Has anyone got this , is the PIC read data prohibited ?
>>
>> Is it still a closely guarded secret?, there were some very clever 
>> and novel ideas used in that slab, in my opinion.
>>
>> Glen
>>
>
> Hi Glen.  I worked on this project, but am an RF/Analog
> guy.  The product line was sold to Symmetricom 20 years
> ago and they didn't continue the E1938A.  At that point,
> there were no closely guarded secrets.  I don't know what
> happened to the source code.  The last contract manufacturer
> for the E1938A was Scotts Valley Magnetics.  You could
> contact them and see if they have the PIC info.  In theory,
> they would have had to have it to program the PIC's.
>
> The most clever thing in the PIC (AFAIK) is the oven
> controller with the double integrator.  "P, I, I^2, D".
> Len Cutler was the mastermind behind this.  I believe
> he leveraged his experience with double integrators used
> in Cs control loops.  I remember him telling me that the
> secret was to have an "anti-windup" algorithm.  Whatever
> he did, the results were phenomenal.  I spent countless
> days in the lab exercising the loop and it always worked
> perfectly.
>
> Rick Karlquist, N6RK
>