Antique ammeter

Discussion in 'General Electronics Chat' started by azog, May 6, 2008.

  1. azog

    Thread Starter New Member

    Aug 29, 2006
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    I recently picked up an old (antique?) ammeter, mainly because it looks cool, but I'm wondering if there is anything I can "do" with it.

    It's a Weston model 155, and you can find a picture here: http://www.humboldt.edu/~scimus/HSTC.27-35/Descriptions/ACVMeter155.htm. In short, this is an AC ammeter, marked from 0-300A. I have a couple of questions about it.

    First, how can I test this? I figured I could shunt this in to my clothes dryer circuit (15A or 30A, I forget), but then again, I might just set the house on fire if I do so.

    Second, this is an AC meter, and I'm not sure of what the difference between meters. From what I can tell (from this website) is that DC meters usually have a shunt resistor, and that is what gives the rating of the meter.

    Is there any way I could use this for a toy, perhaps just driving it with the PWM of an AVR microcontroller?
     
  2. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    Your link describes a voltmeter. Are you sure you have an ammeter? John
     
  3. azog

    Thread Starter New Member

    Aug 29, 2006
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  4. Caveman

    Active Member

    Apr 15, 2008
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    Up to 300A? Hell of a toy!
     
  5. Wendy

    Moderator

    Mar 24, 2008
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    I don't know, monitoring house current perhaps? Kidding of course.
     
  6. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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  7. beenthere

    Retired Moderator

    Apr 20, 2004
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    It should have a shunt to scale it. Changing the shunt will let it respond to lower currents. Think of the fun - scaling the response to 3 amps full scale, but still indicating 300.
     
  8. azog

    Thread Starter New Member

    Aug 29, 2006
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    I guess the better question would be: what is the difference between an AC meter movement (of any sort) versus a DC meter movement? And what makes a meter an ammeter versus a voltmeter?

    For the particular meter I am asking about, I opened it up, and it looks like it's basically a huge magnet that loops around the movement; one end of the magnet starts at one of terminals, loops around the movement, and goes to the other terminal. I can take a picture if that helps.
     
  9. mrmeval

    Distinguished Member

    Jun 30, 2006
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    It either has diodes and filtering to get a representation of the AC current or it uses coil winding techniques to do the same thing.

    You can research the patent if it's on it.
     
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