[time-nuts] App Notes Voltage References
bruce.griffiths at xtra.co.nz
Sun Nov 30 02:01:03 UTC 2008
Steve Rooke wrote:
> 2008/11/30 Bruce Griffiths <bruce.griffiths at xtra.co.nz>:
>> Since these devices actually store the reference voltage on an internal
>> capacitor, it would be interesting/informative to plot the output as a
>> function of time over several years/decades.
>> They haven't yet been available for long enough to establish their long
>> term stability in actual use.
>> I wonder if one can recharge the internal capacitor should this prove
>> necessary or if one wanted to adjust the output?
>> This probably requires access to an internal node.
>> During manufacture, a servo loop adjusts the output by changing the
>> voltage on the internal capacitor until the output reaches the voltage
>> of the external precision reference.
>> The servo loop is then opened trapping the required charge on the capacitor.
> I guess that would require having a suitably accurate measuring
> instrument with an accurate reference voltage in the first place.
> 73, Steve
Not necessarily, a stable (not necessarily having a known absolute
error) standard is required.
If the drift is high enough it could be detected by comparison with a
fresh standard of the same type every few years.
Assuming the manufacurer's specifications can be relied upon.
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