Your digital meter question brings up a good point. Unfortunately, the whole
situation here is a little more complex than you might like.
First, the overall accuracy of your meter is determined by more than the
readout device. In particular, a DVM contains an A/D converter and a voltage
reference, both of which contribute equally to its accuracy. Second, you
cannot accurately, or consistently, make readings with 4 digits of accuracy
on even the best analog meter. If you look at specs on analog meters, you
will hardly ever (never?) see meters with 1% accuracy, but digital meters can
do that regularly. Also, the linearity of electrodynamic panel meters is not
perfect. When I started in electronics, analog meters were considered 5%
instruments at best.
In summary, you cannot make a good decision based upon just the facts given.
I will say that in my experience reputable DVM's are more accurate than 260's
were, and I am not just talking about the 4th significant figure. The issues
of accuracy and resolution are really independent of each other.
As far as your 12-digit calculations based upon your 4 digit DVM readings -
the 8 least significant digits are garbage (or at least 7 of them are - let's
not get into issues about so-called 1/2 digits.)
Keep your slide rule on hand for when your calculator battery dies. If you
use solar powered ones (which I do finally) then you should also keep it on
hand for when the sun wobbles out of orbit, or we do.
Eric K8LV
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