Wolfgang I have quite a collection of equipment and have build Dual Mixer, PICTIC and what I think is best for you a circuit I call the Austron circuit. For less than $ 50 you can have a standalone system that gives you a RS 232 output with 1 E 12 resolution in 1 second, the PIC has 0.1, 1, 10 and 100 second gate time. At 100 seconds you get 1 E 14. The circuit does use a two stage Xtal filter which is the most difficult part of the circuit. How ever a DDS could be used, but the DDS does not give you 1.000100 MHz with 14 digit accuracy so post processing would be needed. If you have uProcessor expertise that would be perfect way to eliminate the filter part, making it even lower cost and much simpler. Never did a DDMTD so I do not know how it compares. If you are interested contact me off list and I send you all information. Bert Kehren In a message dated 4/19/2012 5:41:08 P.M. Eastern Daylight Time, skywatc...@web.de writes:
Hi Bert I want to monitor the frequency deviation continuously (that means: i don't want to look at a scope ;) and log the data several times per second. The goal is not to make a 'quality test' of the oscillator, but to look for frequency deviations which are caused by external influences of various kind. I have a digital 500 MS scope, so i can use this for circuit development, but i don't want to use it for the actual measurements. Time measurements with microsecond accuracy can be done with a microcontroller, that's not a problem. BTW i'm using the Parallax 'Propeller' controller which has 8 cores running at 80 MHz each, and can measure time intervals with 12.5 ns resolution. It has also some very interesting timing circuitry, and can even generate VGA video signals with user-defined timing without any external special components. May be of interest for one or the other here on the list. :) For those who are interested: http://www.parallax.com/Portals/0/Downloads/docs/prod/prop/Propeller-P8X32A- Datasheet-v1.4.0.pdf I think the DDMTD could be a good solution. The question is, if 74HCxx parts would be good enough to get < 1 mHz resolution for a 10 MHz frequency with an update rate of < 1 sec. Can i use a 74HCT4046 PLL for the 'helper PLL' or is this one not good enough ? Maybe i will do some tests next weekend to see what i can achieve with these 74HC parts, before looking for better ones... Regards, Wolfgang Am 19.04.2012 23:14, schrieb ewkeh...@aol.com: > Wolfgang > It would help if you would let us know what equipment other than a scope > you have. Also what resolution you would want to achieve. One time set up or > want to use repeatedly. > Bert Kehren > > _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.