Hi The great thing about a wire wound pot is that as a voltage divider, it has a very low temperature coefficient. The problem with adding resistors is that their temperature coefficient will not match that of the winding material on the pot. The “value” of the wire wound is lost in this case. You might as well just run a multi turn cermet pot.
One alternative are the big multi dial voltage dividers you see from time to time on eBay. Prices (as with anything on eBay) are all over the map. Score some cheap and you can get a lot of resolution and a lot of stability. Another alternative would be to grab some “zero drift” op amps. Buffer up a pair of pots and then drive a thin film network with them. (or spend around $20 each on some shiny new low TC resistors). Then buffer the sum junction with another op-amp. =========== If the oscillators are OCXO’s, ground current is going to make problems pretty quickly. With a common ground pin and voltage changes measured in millivolts, it limits how well a normal OCXO can be set. Bob > On Feb 4, 2020, at 2:18 AM, Perry Sandeen via time-nuts > <[email protected]> wrote: > > Learned Gentlemen, > Thanks for the two references for affordable 10 turn precision pots. > This will allow me to go back to my original and simpler circuit of a series > string of resistors and in that string connecting the 10K10 turn pot in > parallel with one of the resistors, probably a 1K, which will be set by the > upper slightly above and the lower just below the *sweet spot* needed. It > will take a bit of juggling for each oscillator but that will be far simpler > than using 3 digital pots. > Regards, > Perrier > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
