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INA190: Problem with nanoampere current detection with INA190.

german orlando niño uribe
Prodigy 140 points
Part Number: INA190
Other Parts Discussed in Thread: INA199, INA186

Tool/software:

Hello

First of all, thank you for reading this post.

I'm working on designing a circuit for a 10 Gigaohm megohmmeter. The high-voltage circuit works fine with 1000 volts output. I searched online and found the INA190. I decided to use it to test current sensing because it has a low input bias current (0.5 nanoamps). The circuit I have is as follows:

However, I'm experiencing a fairly high noise level on the output, which prevents me from measuring values ​​above 500 megohms. I'd like to know if anyone knows how to correct this situation by attenuating the noise and improving the circuit's response. This is the signal capture with a reference value of 1300 megohms.

I'd also like to know if there are better options for this purpose.

Thank you for your time.

  • +1
    TI__Expert 8040 points

    Hi German,

    1. In your schematic, if you're using the INA190 please change the device from INA199 to INA190.

    2. If you're measuring current across R1, we recommend connecting pin 5 to the other side of R1.

    3. To reduce noise in the signal, please follow our recommendation in the INA190 datasheet, section8.1.3. Adding a differential capacitor will help keep the input line signal constant and if you observe common-mode noise as well, please add capacitors to GND from each input line as well.

    Best,
    Mallika Senthil

  • 0 in reply to Mallika Senthil
    Prodigy 140 points

    Hello Mallika Senthil.

    Thanks for the information. I have a question: Is the INA190 suitable for this application?

  • 0 in reply to german orlando niño uribe
    TI__Expert 8040 points

    Hi German,

    Whether a device is suitable in an user's application depends on the user's requirements (e.g accuracy). In general, the INA190 is one of our most precise devices, and as long as you don't exceed the abs max ratings in the datasheet and your input signal doesn't have frequent switching, it should work in your system. 
    Another device you could look at is the INA186, it also has very low Ib, but has lower precision than the INA190.

    Best,
    Mallika Senthil