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jaywee03
Joined: 13 Jul 2004
Posts: 7
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 20 Jul 2004 18:29 VOLTMETERS and AMMETERS!!! help me pls! badly needed! |
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does anyone knows the history/background of voltmeter and ammeter? its types? and also its innovation. could you tell me a site were i could find it. thanks! i need it badly. thanx again! 
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flatulent
Joined: 19 Jul 2002
Posts: 4856
Helped: 292
Location: Middle Earth
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| 20 Jul 2004 20:09 Re: VOLTMETERS and AMMETERS!!! help me pls! badly needed! |
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The first instruments were very crude and relied on electrostatic repulsion of two foils in a glass jar. You probably have seen drawings of these in the introductory physics books.
Once the connection between current and magnetic field was discovered, the current meter with the rotating pointer was invented. At the same time Ohm's law was used to make volt meters with a resistor in series with the current meter. Various improvements on this mechanical readout were made to include shaping the fixed magnetic field poles for a linear scale factor and using a wire whose torque was the opposing force on the pointer rotation.
These measurement functions were combined in a single instrument called a multimeter which had a mechanical switch to cut in series and shunt resistors and rectifier diodes to select the scale factor. The most famous one is the Simpson brand 260 which is still in production after 65 years or so.
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samcheetah
Joined: 25 May 2004
Posts: 672
Helped: 31
Location: Pakistan
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| 21 Jul 2004 5:34 Re: VOLTMETERS and AMMETERS!!! help me pls! badly needed! |
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just get a good book on electrical measurements and instrumentations
i have studied voltmeters and ammeters from "Electrical and Electronic Measurements and Instrumentation" by J. B. Gupta. but i think that this book is not available outside India and Pakistan. so just get any book on this topic. and if u are able to find this book it will be better.
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