Re: GHz counter

Hi Tim, thank you!

"Tim Shoppa" <shoppa@xxxxxxxxxxxxxxxxx> schrieb im Newsbeitrag
news:1121104887.924952.257930@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> > How to measure the time between signal out and back?
> > Is there an existing project?
>
> What distances is it going to be used at?

around 100 m

>
> For times in the picosecond to hundreds-of-nanosecond range and low rep
> rates, a "Time to amplitude" converter (basically using a capacitor as
> an integrator) followed by an ADC is very simple technology. Dates
> back to WWII radar and probably earlier. There are gotchas with
> switching the current source on and off rapidly and resetting the
> capacitor back to zero charge, but these are lessened somewhat when you
> are in control of the repetition rate/sync.

do you mean a switched integrator?

>
> For longer times, a combination of a counter with a TAC is very
> appropriate. The counter won't have to run in the GHz if you do it
> right.

What is a TAC? I was thinking about 1 Ghz regarding 30 cm resolution...

>
> There are some clever things that can be done with
> multiple-approximation switchable delay lines, too. Not very hi-tech
> (this would be the solution from 40 years ago) but it does work if you
> control the repititions.

I never heard from.

>
> All that said, I would highly encourage you to look at the waveforms on
> a scope before going into too much deail with measuring sub-nanosecond
> times. You'll have to work with discriminators on your sensor, for
> example, and adjusting their threshold depending on path loss (I
> suppose for very short paths this may be a non-issue, the laser
> rangefinding I did was in the several km range) or adjusting laser
> output power to compensate for path loss.

You created a range finder?
>
> Tim.
>


.

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