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