Hi At least the last time I tried it, the filter a square wave / integrate based on a square wave approach both appeared to give performance that was inadequate. Simply put, the triangle wave should give *better* performance than a similar wave generated off of a pair of good oscillators. That was not the case. Could there have been errors made - sure. Exactly what did I do - long time ago, details are in a log book that probably doesn't even exist any more.
Ideally the signal source would be much better than the limiter I'm trying to test. If I want to verify a 10 ns limiter, a triangle wave good to a ns or so would be a nice thing to have. It would also be nice to easily verify that device. The objective is a quick test of a limiter rather than the world's best low frequency R-C oscillator. That of course assumes I can womp up the DAC gizmo easily. Bob On Feb 2, 2010, at 7:58 PM, Joseph M Gwinn wrote: > [email protected] wrote on 02/02/2010 07:20:24 PM: > >> From: >> >> Bruce Griffiths <[email protected]> >> >> To: >> >> Discussion of precise time and frequency measurement > <[email protected]> >> >> Date: >> >> 02/02/2010 07:27 PM >> >> Subject: >> >> Re: [time-nuts] Triangle Waves >> >> Sent by: >> >> [email protected] >> >> 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 > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
