On 07/19/2012 07:36 PM, Al Wolfe wrote:
Chris,
The simplest zero crossing detector would be to feed your 1 volt, 10
mHz from the XL-DC into the input of an IC with schmidt trigger inputs.
You would need to provide a series coupling cap and probably some DC
bias from a pot to adjust symmetry of the output. I would also think
that if you ran the four or six inverters of a schmidt trigger inverter
chip in series that you would get a pretty good square wave out the end.
One circuit I was recommended when I was looking for ideas uses a 1M
resistor to feed the output of the inverter back to the input to
self-bias, like this:
http://partiallystapled.com/~gxti/circuits/2012/07/06-beanpole.png
I'm also trying a discrete approach based on the TADD-2 / T2-mini:
http://partiallystapled.com/~gxti/circuits/2012/07/06-tadpole.png
The latter has definitely been used successfully in timing applications
but the simplicity of the inverter approach is very appealing, so I'm
giving both a test, along with some other miscellaneous GPSDO
components, before proceeding with a full GPSDO.
-- m. tharp
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