CT Secondary low current measurement before giving to ADC

Discussion in 'General Electronics Chat' started by vinoda, May 12, 2018.

  1. vinoda

    Thread Starter New Member

    May 12, 2018
    6
    0
    In ammeter application, I am using CT for step down current value. primary current range is 150mA to 5A an i get secondary current 60uA to 2mA. what kind of circuitry i have to add for low current measurement before giving it to ADC of microcontroller?
     
  2. ericgibbs

    Moderator

    Jan 29, 2010
    5,455
    1,022
    hi vinoda,
    Welcome to AAC.
    What is the value of the burden resistor on the output of the CT.?
    E
     
  3. vinoda

    Thread Starter New Member

    May 12, 2018
    6
    0
    30
     
  4. dendad

    Well-Known Member

    Feb 20, 2016
    1,897
    481
    For one thing, if you run multiple turns through the CT, it will increase the output. That could help.
     
  5. ericgibbs

    Moderator

    Jan 29, 2010
    5,455
    1,022
    hi,
    Across the 30R, you should measure approx 1.8mV thru 6mV.
    Is the ADC of the MCU 3.3v or 5v. ?

    E
     
  6. vinoda

    Thread Starter New Member

    May 12, 2018
    6
    0
    i increased primary number of turns to three. but unable to measure current less than 1mA
     
  7. vinoda

    Thread Starter New Member

    May 12, 2018
    6
    0
    internal voltage reference 1.1v used for ADC measurement. controller voltage 3.3V
     
  8. ericgibbs

    Moderator

    Jan 29, 2010
    5,455
    1,022
    hi,
    The simple option would be a OPA, gain say 1.1v/6mV, approx gain 183.
    I am assuming unidirectional DC current.?
     
  9. vinoda

    Thread Starter New Member

    May 12, 2018
    6
    0
    could you suggest any circuit schematic?
     
  10. ericgibbs

    Moderator

    Jan 29, 2010
    5,455
    1,022
    What type of OPA's do you have in your bits box.?
    E
     
  11. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    8,611
    1,957
    Have you tried increasing the value of the burden resistor?
     
  12. vinoda

    Thread Starter New Member

    May 12, 2018
    6
    0
    i am using CT1231. recommended secondary burden for this ct is 30 ohm.
     
Loading...