[time-nuts] EFC tracking

Raj vu2zap at gmail.com
Sat Jun 26 14:22:00 UTC 2010


Do a simulation and see how your card behaves. I've had some unexpected
results in similar attempts years ago. 

Nothing like an add on card suitable for the job. These cards are not cheap.

>I would like to track the EFC voltage in hardware using something
>cheap and ready to hand. I was thinking of using a sound card as it
>has good resolution but it's obviously only AC coupled so it would not
>measure the DC of the EFC. I thought about modifying a sound card to
>make it DC coupled but most of them seem to reference the 0V point to
>some internal reference voltage hence there is a DC shift there. I
>next thought about turning the DC into AC by chopping it, IE.
>inverting 50% of the voltage via an oscillator. This way I could pass
>the square wave directly into an unmodified sound card, take
>measurements and then do an RMS calculation on them (really just need
>to flip the sign on, say, the negative readings).

Bangalore, India. 

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