Re: very accurate timer

"fragget" <fragget@xxxxxxx> wrote:

> Hello, this is my first post here so here it goes... I'm looking
> for a highly accurate timer, I need one that could measure a time
> in nanoseconds if possible. I figured this would not be impossible
> since the clockspeed of a modern computer is 3 Ghz, which means
> measuring a time up to a third of a nanosecond would be possible.
> However a nanosecond is also fine by me. I really hope someone can
> help me out here on how to get such a component or how to make
> one;)

> Thanks in Advance;)

> Dave

Hi Dave,

If you can use averaging, you can count an accurate clock several
thousand times and average the counts. This is how at least one of
the HP counters worked. The rms error decreases with the square of
the number of counts. This places a practical limit on the minimum
error you can achieve before you run out of time, or the signal
drifts.

If you can use averaging, you can also use the Binary Sampling
technique descibed below. This bypasses the square root averaging
barrier. The example shown is a 1MHz square wave, and using this
technique gave 1 picosecond rms jitter in one second.

Regards,

Mike Monett

Antiviral, Antibacterial Silver Solution:
http://silversol.freewebpage.org/index.htm
SPICE Analysis of Crystal Oscillators:
http://silversol.freewebpage.org/spice/xtal/clapp.htm
Noise-Rejecting Wideband Sampler:
http://www3.sympatico.ca/add.automation/sampler/intro.htm
.

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