Measuring Current using Current transformer

Discussion in 'Analog & Mixed-Signal Design' started by Qual, Sep 18, 2016.

  1. Qual

    Thread Starter New Member

    Aug 5, 2016
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    Hi ,

    i was trying measure current using Current Transformer but i see spikes at the output of transformer and cant see proper waveform on oscilloscope.

    Attached is the waveform...

    Any suggestion.

    I want feed the voltage to Micro controller so that i can display same on LCD.
     
  2. DickCappels

    Moderator

    Aug 21, 2008
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    That waveform is normal for some types of loads, especially capacitor input filters.

    What is the source (AC power line?) and load (input to a power supply or electronic appliance?) for the circuit you are measuring?
     
  3. Qual

    Thread Starter New Member

    Aug 5, 2016
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    Source is AC power line and load right now using a rheostat..! ( 56 ohms)
     
  4. AlbertHall

    Well-Known Member

    Jun 4, 2014
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    The section at the top of the display seems to be showing a sine wave though:
    upload_2016-9-18_9-58-28.png
     
  5. DickCappels

    Moderator

    Aug 21, 2008
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    I am going to take a guess: You are not using a transformer that was designed to measure current or you do not have an adequate shunt. What kind of transformer are you using? What are you using for a shunt? (Shunt: The resistor across the primary that sets the scale)
     
  6. Qual

    Thread Starter New Member

    Aug 5, 2016
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    i am using 56100C current transformer from Murata for measuring current.
     
  7. AlbertHall

    Well-Known Member

    Jun 4, 2014
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    You are way outside the frequency range of that transformer. From the datasheet:
    „ 20kHz-200kHz frequency range
     
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  8. Qual

    Thread Starter New Member

    Aug 5, 2016
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    so i won't be able to measure current ?!! so is that transformer used is wrong ??

    any help pls...
     
  9. AlbertHall

    Well-Known Member

    Jun 4, 2014
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    You cannot use that transformer to measure current at 50Hz. It is intended for switched mode supplies and the like.
     
  10. MaxHeadRoom

    Expert

    Jul 18, 2013
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    What kind of current are you measuring, would a ACS712 work for you, although they are in circuit type rather than transformer, comes with isolation build in.
    The can be had for a couple of $'s on ebay with circuit, 5A, 20A and 30amp ranges.
    Max.
     
  11. Qual

    Thread Starter New Member

    Aug 5, 2016
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    i want to measure the AC and DC current. Want to build my own circuit.... so this attempt
     
  12. MaxHeadRoom

    Expert

    Jul 18, 2013
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    The ACS712 measures AC & DC current and can be purchased as a bare IC, you still usually need some kind of interface.
    Max.
     
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