Jeff Wisnia wrote in
et:

Homer J Simpson wrote:

"Jeff Wisnia" wrote in message
et...


I believe the ammmeter is what I used to know as a "moving iron"
type, and IIRC the restoring force was supplied by some kind of
permanant magnet field, not by a mechanical spring. Am I right about
that?


Nope. Still a spring.

http://www.tpub.com/content/doe/h101...h1011v4_76.htm

Moving iron vane - The moving iron vane meter operates on
the principle of magnetic repulsion between like poles. The
measured current flows through a field coil which induces a like
magnetic field into a fixed and moving vane causing the
moving vane to deflect a pointer in proportion to the
current or voltage applied to the coil.



I hear what you say about a spring, and it makes sense that there may
be one there. But it's interesting that the reference link you gave
mentioned "springs" when describing the first two meter types, but not
the moving iron one. Wonder why? Probably just an oversight.

Jeff (Who is NOT going to tear that old meter on the Eico 1050 apart
to find out.)


You can test for a spring without dissection. First, does the meter jump to
a position and oscillate a bit before settling? If so, put your ear (or a
stethoscope) to the meter panel and tap it sharply. If there's a spring in
there it should ring like a bell. If you see that resonace in the meter
movement, yet hear no spring, then you and Homer are probably right, the
spring would be entirely magnetic.