Teasing? Tempco? What tempco.
I think my tweaking efforts should end on -0.018 ppm/K, based on
Live SVG data from today run. at that reaching 3458A resolution/noise already even with 32C span. Next step is 10V output stange tuning.
I don't need any more parts for USA Cal club FX ("wish to say that for rest of them, eh"), so it's just testing time and then initial 200 hours monitoring to see that reference settled.
Then calibration to my lab DC Volt (that is, measurement only). Then another 800 hours to make sure everybody happy and stable, final TC characterization with everything assembled, noise measurement and then it's ready. So if all goes well, that is 50 days from now. I don't think rushing anything with LTZ1000A-based reference make any sense at 500$ reference.
Also how about 10KOhm standard for USA Cal Club? There is
L&N 4030 measured 10000.215 Ohm (+/-8ppm max abs) that just sits, doing nothing. This is giveaway resistor, I bought it specially for USAC needs, it was just $50.