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INA199: AC Current sensing with Current transformer

Eazhil Arasan1
Prodigy 10 points
Part Number: INA199

Hello,

I've tried to use INA199A1 for measuring the AC current sensing using the Current transformer, and I've attached the schematic from google source. 

Now, I'm receiving output from the same circuit, but my prob is the output with 50/5 CT or any other CT was non-linear in which I can't able to measure the linear output with Microcontroller, it is difficult to show the proper output with the display. Instead of R1 and R33, I've used only one 0R10/2010/1% resistor because I need to measure the current with 1000/5 CT.

I also tried with INA181A1 with the same circuit also receiving the same prob, kindly please suggest a solution to resolve the prob.

Thanks in Advance,

M.EAZHILARASAN

  • 0
    TI__Mastermind 32260 points

    Hello  M.EAZHILARASAN,

    I have a couple of questions.  The questions may lead to you finding your answer.

    Do you have a DC bias on the sense side of your current transformer?  I would assume from your schematic it would be from a parasitic DC GND connection from C27 or C28 or through our INA199 (not recommended).  This is a concern as this could violate the Common mode input range as thing are moving around.  Be careful if you attempt to measure this as you could add a DC bias with your measurement instrument.

    Another question are about FB5,FB4, R32, R31 with an input bias current on INA199 being 28µA and this value can change with input voltage or Common mode voltage changing this could impact your measurement.  We have a section in the datasheet that makes a recommendation that the resistance should be smaller than 10 Ω.  See section 8.4.1 in the INA199 datasheet.

  • 0 in reply to Javier Contreras4
    TI__Mastermind 27715 points

    Hello M.EAZHILARASAN,

    It's been some time since your post. If you still need help, please reply with answers to Javier's questions so he can continue to assist you.

    Best regards,

    Ian Williams
    Applications Manager
    Current Sensing