• State
  • Locked Locked
  • Replies 3 replies
  • Subscribers 48 subscribers
  • Views 933 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

INA226: INA226 accuracy

Homer
Prodigy 130 points
Part Number: INA226


Hello, 

Now we are using the INA226 to measure the current by using 20mohm+/-1% shunt resistor in design. We have two questions about it. 

1. How to get the current accuracy according to INA226 datasheet in theory?

2. When we do current measurement for a constant current source, we find the measurement value will be slowly increased over time. For example, measure the 3A@5V. The measurement value will change from 3.024A, 3.025A, 3.026A, 3.027A ...... and so forth. 

So could you help to respond to above questions?

Thanks, 

Best Regards, 

  • 0
    TI__Mastermind 23235 points
    Hi Homer,

    To understand the theory behind current gain error, I would start with our video series which can be found at the link below. Specifically, videos 5-12 will talk you through all the different types of error you will encounter and how to combat them in your design.

    e2e.ti.com/.../467332

    As for the constant increase, this is peculiar. Does it ever level out, or is it a constant increase? How quickly do the mA's tick up, is it a relatively fast process? Finally, what kind of supply are you using to send the constant current?

    Carolus
  • 0 in reply to Carolus Andrews
    Prodigy 130 points

    Hi Carolus,

    Merry Christmas.

    Thanks for your info. I will check the vido for the 1st question.

    As to the 2nd question, we are designing the INA226 after 3.3V and 5V DC-DC output to measure the current and voltage. In testing, we are using a e-Load to sink current. The e-Load is Chroma 63103. we are using its CC mode to sink a constant current, 3A.

    So when we sink current by using the loading, we find the measurement value from INA226 is gradually growing up. We will read the value per 1s. The value is increased inevery reading.

    We checked the voltage drop on the shunt resistor, 20mohm. The voltage drop is stable. So it looks the change must be from INA226 inside. By the way, in design, we are using the filter recommended in datasheet, figure 22. INA226 with input filtering, page 12, we are using 6.8ohm and 0.1uF on differential input.

    Homer

  • 0 in reply to Homer
    TI__Genius 15760 points

    Hi Homer,

    Can you please measure the voltage drop on the input pins of the device instead of shunt resistor? We want to verify if there is any losses in the input traces.

    Measure the differential voltage between IN+ and IN- and measure the voltage in the shunt resistor. Are the numbers equal? If not, how different? Please send us a table with your results for further support. 

    Regards