Michael Watterson wrote:
> 1kV needs 1M Ohm for 1mA, More than 4M7 precision resistors are
> expensive. Calculate assuming 4M7 resistors and 47k Ohms. The
> tolerance of the 47k Ohm resistor can be much worse than the 4M7 as
> you are dividing by 100

Huh?  At divide ratios well above or below 1/2, the error of both resistors
are added to make the divide ratio error.  At a divide ratio of 1/2 the
errors are only weighted by 1/2 instead of near 1.  In no case does the
error a resistor in a resistor divider have a effect on the divide ratio at
less than a weighting of 1/2.

Think about it.  Do some examples if that helps.

--=20
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.