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Jeff Wisnia <jwisnia@xxxxxxxxxxxxxx> wrote in
news:Mt2dnbI78os5YIfYnZ2dnUVZ_vmdnZ2d@xxxxxxxxxxxxxx:
> Homer J Simpson wrote:
>
>> "Jeff Wisnia" <jwisnia@xxxxxxxxxxxxxx> wrote in message
>> news:zLydnZVzrJEpLYfYnZ2dnUVZ_tWdnZ2d@xxxxxxxxxxxxxxxxx
>>
>>
>>>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/h1011v4/css/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.
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