Bill, On 27 June 2010 01:21, WB6BNQ <[email protected]> wrote: > Steve, > > I think using a voltage-to-frequency converter would solve that problem. They > are not too expensive and there are several flavors from Amalog devices and > some > others.
I just had one of those duh! moments :) It does make the sampling a little more complicated as I'd have to take a number of samples and do something like a FFT to get the frequency, I think. My idea seemed just a simple way to just make a single, or limited number, of sample(s) and I have the data. Still, this is a good idea and I'll have a good thunk about it. > Just set it for a 1KHz start point or maybe 10KHz. Thanks for your advice, Steve > Bill....WB6BNQ > > > Steve Rooke wrote: > >> 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 >> >> ------------------------------------------------------------------------ >> Name: DCchop.png >> DCchop.png Type: PNG image (image/png) >> Encoding: base64 >> >> ------------------------------------------------------------------------ >> _______________________________________________ >> 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. > -- 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.
