[time-nuts] HP5065A C-field mods and optical unit mods

Bruce Griffiths bruce.griffiths at xtra.co.nz
Tue Nov 21 15:40:31 EST 2017

What is the effect of the C-field coil dimension tempco?

At some point this will surely dominate overthe coil current tempco.


>     On 22 November 2017 at 09:16 Charles Steinmetz <csteinmetz at yandex.com> wrote:
>     Luciano wrote:
>         > > 
> >         what you refer is the resistance relation referred to the LM299 source around 14VDc but you have to consider
> >         the tuning range of the pot, in the original HP5065A is 2E10-9.
> >         Of course, it depends on the setting value of the variable resistance, but you have to consider a possible variation of 20PPM/c on 2E10-9.
> > 
> >     > 
>     No, you don't. The tempco that matters is the aggregate tempco of the
>     series string. Only a very small portion of the string voltage appears
>     across the pot, so a 20ppm tempco of that small part will cause a much
>     smaller change in overall tempco of the series string.
>     Perhaps Corby will tell us what value the pot is, and then you can
>     calculate the aggregate tempco of the string at various pot settings and
>     see for yourself.
>     Charles
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