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measuring ac

Discussion in 'General Electronics Discussion' started by mogli_06, Sep 14, 2013.

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  1. mogli_06


    Sep 20, 2012
    sir i would like to pose a question regarding ac current measurement.If
    1. I measure it with a centre zero volt meter then does the pointer oscillates as it is in the sinusoidal waveform?
    2. I measure it with a digital multimeter how does its how 220V (indian domestic supply) even it is a sinusoidal wave form and keeps on oscillating showing different voltages at different points?

    Would you please clarify this doubts for me?
  2. john monks

    john monks

    Mar 9, 2012
    1. If your analog current meter is in the DC mode (direct current) then the needle will oscillate and you may be able to see that. If the meter I'd and AC (alternating current) then the needle will raise to some level.
    2. Similar thing happens with a digital meter. But in the AC mode internal rectifiers convert the AC to DC and a capacitor charges up and maintains an even voltage that is read by the digital portion.

    Now I hope you are trying to measure voltage and not current because in the current mode your meter will be destroyed if you place it on a voltage source such as the 220V you have in India.
  3. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    At 50 Hz neither an analog nor a digtal meter will show you the oscillations you expect. In DC mode both meters will show 0 V because they are unable to follow the rapid oscillations.
    Even if they did, your eyes couldn't follow the movement of the pointer or the change in difits. All you could see is a blurred image.
    Remember: 24 pictures a second are enough to trick the eye into seeing a movie instead of a sequence of images.

    To see the waveform, you need an oscilloscope. And dont connect the scope's probes directly to 230V mains!
  4. shreya


    Jul 27, 2013
    y dont u try measuring it on a cathode ray oscilloscope .... dat must come out to be helpful maybe
  5. davenn

    davenn Moderator

    Sep 5, 2009
    read Harald's post, that's what he suggested :)

  6. mogli_06


    Sep 20, 2012
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