This also applies to the plate meter or any low-resistance current meter,
which nearly all of them are.
73, Bill W6WRT
Good info Bill -- and it's not a difficult exercise, beyond simple algebra
to solve for the right series resistance value once the meter resistance is
known or computed.
To validate a DC meter's internal resistance, I still use the simple method
described in a ca. 1950s Allied's Electronics Data Handbook. It always
brings me back to my high school days when as students, we were tasked to
find a DC meter's resistance. First thought for the unknowing: just grab a
<gasp!> Simpson 260 set on the Rx1 scale! The instructor stopped us in
time. Anyway, that same math will also prove why sensitive moving coils are
subject to failure without the limiting resistor.
Paul, W9AC
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