Hi HighVoltage,
ok, I assume that you still let your '470As run 24/7.
Therefore, they are inside specification, for 10V dc, i.e. 16ppm / 1yr., 20ppm / 2yrs., and you've seen 10 and 14ppm after 1 1/2 years.
If you subtract these 8ppm of 'basic accuracy' for 24h, you get about these 8ppm/yr. and 14ppm/2yr. specs of the 3458A, caused by the same violated LTZ1000A @ 95°C (+).
Metrology grade instrument? Nope, neither is the 470A, nor the 3458A, only because of that LTZ reference.
And because the 470A has the same 6 1/2 hardware (these 8ppm..) on the main board, and no real artifact / ACAL calibration to compensate for that, it's a good and bit more stable 34401A replacement, but nothing more.
If you have real 'guts', (.. Olli Kahn ...), then you may pimp your LTZ references to 12.5k/1k or 65°C, and send them off for re-calibration and adjustment, and live happily with < 2ppm/sqrt(yr) ever after.
Hi TiN,
I doubt that KS will ever design a successor.. the 470A is good enough for that industrial market, at least on paper.
Also, all of the old eggheads left the company, or pitiful passed away..
But if they do, they really should keep the existing ACAL procedure, but add Vishay BMF resistors (or something like FLUKEs hermetic TF arrays) all over the place, like inside the Fluke 8508/58/88, AND should consult us for a much better LTZ reference. (Daniel B., did you hear the prophecy?)
Such a model update would also silence this certain ACAL denier
Frank