bw wrote:
"Antonio Vernucci" wrote
What amazes me is that I could not find any visible adjustment point (e.g.
a variable magnetic shunt). Evidently they were able to produce very
precise meters requiring no adjustment.

"bn" wrote
Good find. Better quality meters were rated to 1 or 2 percent at FULL SCALE.
Also, many are rated for mounting on a steel panel. Many are not so rated.
The presence of external magnetic fields WILL affect the reading. snip


Hi,
I picked up a Weston type 301 5mA d.c. meter marked for use
with a 1/8" steel panel.
I find it takes about 6.1 mA to deflect to full scale
without a panel. That sounds as if the presence
of a surrounding steel panel would increase the meter sensitivity
by about 20 percent.
Could someone explain this, please?

Thanks,
Ed Knobloch