electronic weighing machines

Discussion in 'General Electronics Chat' started by kahafeez, Dec 20, 2008.

  1. kahafeez

    Thread Starter Active Member

    Dec 2, 2008
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    i 've been wondering how do the electronic weighing machines work...... like how do they measure the weight of an object..... may be its a mechanical process bt how do they display that weight on an LCD or 7 segments.... anyone has any idea???
     
  2. mik3

    Senior Member

    Feb 4, 2008
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    Maybe a variable resistor which varies as more weight gets on the scale, then a microcontroller with a built-in ADC to control the LCD.
     
  3. beenthere

    Retired Moderator

    Apr 20, 2004
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    They use a load cell (or several) under the platform. For lab balances, a servo controller maintains the platform at a fixed position by regulating current through a coil that reacts against the field of a magnet.
     
  4. KL7AJ

    AAC Fanatic!

    Nov 4, 2008
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    There are many ways of doing this, but one of the most accurate is with a load cell. This is a bar of linearly elastic material (such as a steel wire or rod) with a resistance wire tightly bound to it. As the rod stretches, the resistance wire does also, increasing its resistance. (In some heavy industrial applications, the resistance of the elastic bar itself is measured)

    Eric
     
  5. bertus

    Administrator

    Apr 5, 2008
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  6. KMoffett

    AAC Fanatic!

    Dec 19, 2007
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    I had a "digital" bath room scale. The weighing mechanism was the same old spring/level/gear system as in the rotating-dial "analog" scales, except the dial had radial stripes. This, with a photo-coupler, fed a quadrature decoder and up/down counter that drove the digital display. Yeah, real digital accuracy. ;)

    Ken
     
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