The human ear is incredibly sensitive to frequency especially when two or more notes are played simultaneously. There is a large group of people who build analog music synthesizers and the oscillator designs are fairly complex and very very accurate. Music synthesizers use a scaling of one volt = one octave of pitch change so there is accurate exponential conversion in the circuit too These are meant to be played in hot nightclubs as well as air-conditioned studios to temperature stability is good. Here is one commercial example ($450) http://www.synthtech.com/motm300.html There are a lot of circuits in the public domain -- the old patents have expired. Here is Dr. Moog's last oscillator - the 921: http://experimentalistsanonymous.com/diy/Schematics/Oscillators%20LFOs%20and %20Signal%20Generators/Moog%20921.jpg Some of the chips are no longer available so do not plan on copying this circuit. There are two differential pairs with additional transistors -- one is used for exponential conversion, the other for sine shaping. Dave > -----Original Message----- > From: volt-nuts-bounces@febo.com > [mailto:volt-nuts-bounces@febo.com] On Behalf Of Charles P. Steinmetz > Sent: Monday, July 29, 2013 14:09 > To: Discussion of precise voltage measurement > Subject: Re: [volt-nuts] Voltage to frequency > > Joe wrote: > > > Since it is relatively easy and inexpensive to have a very accurate > > frequency standard at home, I wondered how difficult would it be > > to use that standard to create an accurate voltage standard. > > > > * * * Since this method apparently isn't being used, > > there must be some reason. Can anyone enlighten me? > > As others have said, it is the [in]accuracy of V/F converters and the > complexity of having to make two accurate modules instead of just > one. In somewhat more detail: > > The V/F conversion can be done open-loop or closed-loop. Let's say > that from the perspective of a time nut, interesting voltage > measurements/standards begin at 1ppm. An open-loop solution can't > come close to that, particularly over temperature and time. On the > other hand, a closed-loop solution requires building what you are > after in the first place -- a very accurate voltage reference and > comparator -- so why bother with the VFC? > > When someone designs an open-loop VFC that is linear and accurate to > better than 1ppm over voltage, temperature, and time, we might have a > different conversation. > > Best regards, > > Charles > > > > _______________________________________________ > volt-nuts mailing list -- volt-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/volt-nuts > and follow the instructions there.