[time-nuts] FE-5680A Mechanical Question
EWKehren at aol.com
EWKehren at aol.com
Fri Jan 13 17:19:18 EST 2012
Are we not overdoing it. 7E-13 for $15 KISS, and if you want to go beyond
that use a $ 30 analog version.
Looking right now at 1 E -14, I do se temperature influences, with my heat
sink stable to .1 C. Mainly due to the fact that is only one side of the
unit and it is clearly designed to use all sides for heat dissipation.
In a message dated 1/13/2012 5:02:48 P.M. Eastern Standard Time,
lists at rtty.us writes:
What we are talking about is toggling the least significant bit in the DDS
to achieve a resolution of less than that LSB. It could be done to a set
period (like a PWM) or pseudo randomly to reduce the noise signature.
Either way, roughly a 16 element long "period" should be quite adequate.
7x10^-16 / 16 would give us a 4x10^-14 step and a 2x10^-14 max error.
On Jan 13, 2012, at 4:30 PM, Don Latham wrote:
> Oh, I hate to be a pedant, but are we talking about dithering, that is
> random perturbations to remove things like hysteresis, or using the
> finite steps as a bang-bang servo?
> Charles P. Steinmetz
>> Bert wrote:
>>> wrong there is no DAC involved, it is a DDS
>> Ahh. Not so simple, then. I still don't much like the notion of
>> dithering, but it may be the only alternative. Or, as has also been
>> suggested here, add a manual C-field adjustment (but that would not
>> change the fact that the RS-232 adjustments would still be ~ 7e-13
>> Best regards,
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> "Neither the voice of authority nor the weight of reason and argument
> are as significant as experiment, for thence comes quiet to the mind."
> R. Bacon
> "If you don't know what it is, don't poke it."
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> Dr. Don Latham AJ7LL
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