I am commenting on my own comment :) I have been using a similar kit from TI for the MSC1210Y5 processor (originally Burr-Brown, acquired by TI since). It was $50 and worked great. I have since made several projects at work using the chip.
Unfortunately, the MSC1210 kit is no longer available, but the new kit is even cheaper. Didier > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of Didier Juges > Sent: Saturday, June 26, 2010 10:20 AM > To: 'Discussion of precise time and frequency measurement' > Subject: Re: [time-nuts] EFC tracking > > Steve, > > You may want to check the "Analog Devices MiniKit for > ADuC702x-series". > > http://www.google.com/search?q=Analog+Devices+MiniKit+for+ADuC > 702x-series > > This kit includes a 24 bit ADC and integrated ARM processor > in a small PWB with all the tools and sample code to do what > you want with very little code to write (you can probably use > the sample code as-is). > > The kit is $30 (or $35, depending on where you look...) and > you will easily spend that much building something that will > not work as well using your sound card. > > Sound card ADCs are intended for audio, and I'll bet their > linearity does not come close to that of the ADuC702x series, > if you can even get the spec for it. > > Didier > > > -----Original Message----- > > From: [email protected] > > [mailto:[email protected]] On Behalf Of Steve Rooke > > Sent: Saturday, June 26, 2010 7:13 AM > > To: Discussion of precise time and frequency measurement > > Subject: [time-nuts] EFC tracking > > > > I would like to track the EFC voltage in hardware using something > > cheap and ready to hand. I was thinking of using a sound card as it > > has good resolution but it's obviously only AC coupled so > it would not > > measure the DC of the EFC. I thought about modifying a > sound card to > > make it DC coupled but most of them seem to reference the > 0V point to > > some internal reference voltage hence there is a DC shift there. I > > next thought about turning the DC into AC by chopping it, IE. > > inverting 50% of the voltage via an oscillator. This way I > could pass > > the square wave directly into an unmodified sound card, take > > measurements and then do an RMS calculation on them (really > just need > > to flip the sign on, say, the negative readings). > > > > I wonder if anyone has done something like this before and > could share > > their experiences. I've attached a diagram image (hope it > is accepted > > by the list) which is my first go with Eagle so I'm not > exactly very > > familiar with it, sorry. The R's and C's in the astable > would be set > > to a clock frequency that enables this to work without bias > given the > > sampling frequency. I'm not sure if this clock should be > slower than > > the sampling frequency or higher, just haven't got my head > around that > > yet. The R's around the op-amp would need to be set in a ratio that > > transforms the EFC voltage into the range that the sound card can > > handle (that is yet to be calculated by measuring the > limits). If you > > have any suggestions or ways of doing this in a better way, I'd be > > very grateful for the advice. > > > > Thanks, > > Steve > > -- > > Steve Rooke - ZL3TUV & G8KVD > > The only reason for time is so that everything doesn't > happen at once. > > - Einstein > > > > > _______________________________________________ > 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.
