[time-nuts] Neutrinos not so fast? (defectove connector)
davidwhess at gmail.com
Thu Feb 23 16:49:17 UTC 2012
A transformer or differential signaling would also have the virtue of
allowing easy galvanic isolation to prevent ground loops.
Fiber optic and line receivers often set their switching threshold
using a positive and negative peak detector. The same design works
very well for analog peak to peak automatic triggering in
AN47-59, 50 MHz Adaptive Threshold Trigger Circuit:
AN61-15, High Speed Adaptive Trigger Circuit:
On Thu, 23 Feb 2012 16:01:55 +0100, Azelio Boriani
<azelio.boriani at screen.it> wrote:
>To square a sine 10MHz you can use a 4:1 transformer with the center tap:
>connect the tap to GND and use a differential line receiver (ADM485,
>MAX485) connected to the differential signal that comes out from the
>transformer. The input of the transformer receives the single ended sine
>On Thu, Feb 23, 2012 at 3:51 PM, Azelio Boriani <azelio.boriani at screen.it>wrote:
>> And by using a differential pair is like halving the rise time: when one
>> arm rises the other falls, effectively doubling the speed of the crossing
>> and the sharpening of the trigger event. Sort of auto_ schmitt_trigger...
>> On Thu, Feb 23, 2012 at 3:45 PM, Azelio Boriani <azelio.boriani at screen.it>wrote:
>>> I recommend the differential pair: here the trigger have to sense the
>>> crossing of the two signals and this crossing is well definite.
>>>> Darn those finite rise times<grin>
>>>> I've been bitten more than once by this very phenomenon (which I admit
>>>> doesn't say a lot for me.. being bitten once is ok, but since I've had
>>>> multiple bites...)
>>>> But this brings up an interesting time-nut problem for the hive mind..
>>>> If you had to design some scheme for interconnecting "boxes" and wanted
>>>> to transmit an accurate time sync, what should it look like, so that you're
>>>> insensitive to things like rise time.
>>>> (maybe this harkens back to the discussion about 10 MHz, why sine vs
>>>> square wave distribution)
>>>> It has to be a single signal (maybe a differential pair), because
>>>> otherwise, don't you have potential for skew between the multiple signals.
>>>> Zerocrossing sort of works, if you take only one direction, but does
>>>> asymmetry of the waveform screw you up? (e.g. what's "zero".. is it half
>>>> way between peak values + and -?)
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