[time-nuts] Triangle Waves
Joseph M Gwinn
gwinn at raytheon.com
Wed Feb 3 00:58:47 UTC 2010
time-nuts-bounces at febo.com wrote on 02/02/2010 07:20:24 PM:
> From:
>
> Bruce Griffiths <bruce.griffiths at xtra.co.nz>
>
> To:
>
> Discussion of precise time and frequency measurement
<time-nuts at febo.com>
>
> Date:
>
> 02/02/2010 07:27 PM
>
> Subject:
>
> Re: [time-nuts] Triangle Waves
>
> Sent by:
>
> time-nuts-bounces at febo.com
>
> Magnus Danielson wrote:
[snip]
> > Just a reality check question here... a simple triangle oscillator is
> > very easily created by two op-amps, one for an integrator and one for
> > Schmitt trigger operation. If you want better long-term stability open
> > the loop and insert a 10 Hz from your favourite divider chain of a
> > trusted 10 MHz or so. Would such a design be limiting your measurement
> > goals considerable, and would any flaws be reasonably to overcome by
> > better design?
> >
> > Cheers,
> > Magnus
> >
> For beat frequencies in the 1-100Hz range one only need verify the ZCD
> jitter and delay variations etc., to within a few nanosec.
> In the short term such jitter tantalisingly close to what a well
> designed audio oscillator is capable of.
> Unfortunately the trigger jitter in most counters is very large for
> frequencies in this range so verifying the low jitter of an audio
> oscillator requires using a ZCD or equivalent.
Would integration of a 50% duty cycle square wave generate an adequate
triangle wave? Modern opamps make pretty good low-noise integrators,
although one would need to use a good integration capacitor to ensure
linear ramps.
The square wave would come from a simple binary divider chain, which will
clean many things up and ensure a stable duty cycle, whatever the nature
of the original signal source.
Joe Gwinn
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