Current sampling circuit

Discussion in 'The Projects Forum' started by Jonesy, Apr 11, 2011.

  1. Jonesy

    Thread Starter New Member

    Jul 7, 2010
    Hi everyone, I've been trying very hard to contruct an analog front end to measure current with an MCU. Translating them into positive 0-5V.But find no luck as the I need a wide range and good resolution of 5mA.

    Requirements :-

    Line current : 0 - 10A 50/60hz AC
    Resolution :5 mA

    I need to translate them into 0-5V to be measure by my MCU to graph the instananeous current waveform, and of coz the rms values, peaks and so on.

    The biggest problem is the 5mA requirement.Any help is greatly appreaciated.
  2. wayneh


    Sep 9, 2010
    You need a minimum of 2000 steps to get to 10A in 5mA increments. That means you need at least 11-bit resolution (2^11 = 2048). I use a LabJack U3 for data acquisition, and it offers 12-bit resolution. So it should be up to the task.

    At that "low" frequency, you could consider a sound-card based oscilloscope. I have no idea what resolution the ADC in a sound card offers, but 12-bit wouldn't surprise me. I think I've seen 16-bit sound cards?
  3. Jonesy

    Thread Starter New Member

    Jul 7, 2010
    I can use an external 12-bit ADC if needed.
  4. t06afre

    AAC Fanatic!

    May 11, 2009
    I would perhaps recommend a current transformer. You will find plenty of information on google. Connecting directly to mains voltage is quite unsafe