25 Jul
2012
25 Jul
'12
5:47 p.m.
Tolerances on carbon comp resistors matter. If you
think that by
buying 1000 20% carbon resistors you'll get 100 that lie within 5% of
the marked value, you'll be sore disappointed. It seems counter-
intuitive, but comp resistors were "cherry picked" by value during
the manufacturing process.
In the early days, they were cherry picked for values, but as the
industry matured, the processes allowed the makers to produce to
whatever value they wanted. If you open a sealed bag of carbon
resistors and measure them all, they will likely all be very close in
value, often with none straying more than 1 percent from any other in
that batch. And over time they all seem to drift with remarkable
accuracy as well.
And who the hell uses 20 percent resistors, other than those old time
1940s and 50 crap table radios?
--
Will