[time-nuts] tbolt temperature coefficient & RMS values (as calculated in LH)

Sarah White kuzetsa at gmail.com
Fri Dec 21 04:51:18 UTC 2012

On 12/11/2012 10:33 PM, Charles P. Steinmetz wrote:
> I initially thought the third unit's oven controller was broken (low
> gain).  Then I noticed that the great majority of posted Lady Heather
> plots appear to be from units similar to that one, with the much higher
> tempco and reversed tempco sign compared to my two low-tempco units.
> But I have seen a few other plots that appear to be from units similar
> to my first two.  The two with the low tempcos do not appear to be
> inferior to other Tbolts with respect to stability, PN, or aging.

I'm pretty sure LH estimates the temperature coefficient in a rather
inelegant way:

Seems based on the graph / display window, and affected by filtering
(RMS is affected by display filtering too) I've been doing measurements
this past week, and posted the first set of results here:


As you can see, with minimal, or filtering completely disabled, LH has a
significant jitter problem in the tempco, and sometimes even shows a
reversed sign.

In my testing, a high or low time constant seemingly has no effect on LH
ability or inability to mangle its calculation of the temperature

The time constant just happens to be 4096 in this case because I'm doing
long-term measurements on the effects of using a value other than 100,
and ultimately employing a binary search algorithm to determine the most
optimal time constant for the crystal in this particular thunderbolt.


More information about the time-nuts mailing list