DC Ammeter Sensitivity Increased?

Nope. Still a spring.

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.)

--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
"Rudeness is the weak man's imitation of strength."

Perhaps they felt it was redundant. It's like holding two magnets N to N and S to S - you are the spring holding them together.

Jeff Wisnia wrote in news:Mt2dnbI78os5YIfYnZ2dnUVZ snipped-for-privacy@conversent.net:

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.

The pointer itself might ring with the test I described, but dull sound, not the sustained ring you'd likely hear from a spring designed to maintain a pointer position.

Hit the 'Back' link at the top of the page above and you'll see the spring.

-- Graham W

PGM-FI page updated, Graphics Tutorial WIMBORNE Wessex Astro Society's Website Dorset UK Info, Meeting Dates, Sites & Maps Change 'news' to 'sewn' in my Reply address to avoid my spam filter.

No.

John

Hello John,

Then maybe the meter was calibrated so it would adjust the indicated current according to the consumer price index. Now wait, with a build date of 1965 that doesn't computer either...

--
SCNR, Joerg

http://www.analogconsultants.com

Also comes to mind that if there is a magnetic pointer restraint this is unusual, and perhaps the meter would (as usual) have bal;ance weights to restore to zero, so perhaps it is calibrated for when the meter face is vertical (panel mount style)? A moving iron movement responds to RMS so waveform should not be a problem.

Peter Dettmann

Got it, thanks!

Jeff

--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
"Rudeness is the weak man's imitation of strength."

FWIW I just went down and tried an orientation test with the meter reading 5 amps and the pointer stayed in the same position whichever way I tipped the unit.

Jeff

--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
"Rudeness is the weak man's imitation of strength."

[snip]

When I worked as a meter tech for EIL many years ago we calibrated iron vane meters of various types. Most of them had a moveable metal piece that could be adjusted to affect the calibration. Most of these meters were made to be opened easily for repair and adjustment and scale changing, but some (GE I think) had an aluminum band that was swaged on with a special tool to seal the meter. All iron vane meters I worked on were for AC use, but they might work on DC. I never tried. However, I think they relied on magnetic induction which is an AC phenomenon, similar to a motor.

The really cheap meters were Shurite, and they used (I think) a permanent magnet moving vane in a fixed coil. These were often DC meters used in automotive and battery charger applications. The permanent magnet might weaken with age, but I think that would make the meter read lower, rather than high. If there were no magnetism, it would read zero. All meters I worked on had springs (taut band types use the band as a spring). A weak spring could cause a high reading.

The only meters I know to be true RMS are dynamometer types, which use a moving coil as well as a fixed coil. When the coils are wired in series or parallel, they read voltage or current. When the coils are separate, the meter can be used as a wattmeter.

Of course, most such measurement is now done digitally, but it is interesting and educational to understand the older technology. Also, many of the lab grade meters were beautiful works of art, with varnished oak or bakelite cases, and carefully drawn mirror scales to reduce parallax, and to obtain accuracy to 1/4% or better.

Paul

On Thu, 28 Sep 2006 10:11:06 -0700, RST Engineering (jw) Has Frothed:

Use a news reader that can mute quoted text.

--
Pierre Salinger Memorial Hook, Line & Sinker, June 2004

COOSN-266-06-25794

On Thu, 28 Sep 2006 18:51:06 +0000, Rich Grise Has Frothed:

Show RFC where quoting is a shortcoming. It's up to the individual to skip over or mute quoted content.

Go f*ck yourself.

--
Pierre Salinger Memorial Hook, Line & Sinker, June 2004

COOSN-266-06-25794

*plonk*

Tim

Consider the blind - who listen to Usenet. They have to wade through a mountain of crap to hear one line - or sometimes none.

RFC 1855, "Netiquette Guidelines",

Section 3: One-to-many communication (mailing lists, netnews), 3.1 User guidelines 3.1.1 General Guidelines for mailing lists and NetNews [bullet 10]: If you are sending a reply to a message or a posting be sure you summarize the original at the top of the message, or include just enough text of the original to give a context. This will make sure readers understand when they start to read your response. Since NetNews, especially, is proliferated by distributing the postings from one host to another, it is possible to see a response to a message before seeing the original. Giving context helps everyone. But do not include the entire original! I take this as saying that quoting, when used in moderation to carry forward the essential context of a thread, is Good, and that when used to excess (quoting the entire original, or the whole thread), is Bad.

--
Dave Platt                                    AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
  I do _not_ wish to receive unsolicited commercial email, and I will
     boycott any company which has the gall to send me such ads!

On Fri, 29 Sep 2006 00:53:00 +0000, Dave Platt Has Frothed:

Right in moderation is the key.

--
Pierre Salinger Memorial Hook, Line & Sinker, June 2004

COOSN-266-06-25794

"The Demon Prince of Absurdity" wrote in message news: snipped-for-privacy@hell.corn...

If I kill-filed everyone who was too clueless to post correctly it would be a lonely place.