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INA226: Current monitor of 0~200A with 0.01A resolution

Danilo A.
Mastermind 24695 points
Part Number: INA226
Other Parts Discussed in Thread: INA238, INA228, INA239, INA229

Hi Team,

We have received this inquiry from our customer.

I want to select INA226 to monitor the current of 0~200A with 0.01A STEP. COMMON MODE VOLATAGE is 12V. Please make sure the parts are suitable. And is there no need for an external comparator circuit or amplification circuit? If not, are there any parts you can recommend?

It seems that our customer needs a programmable gain amplifier with 10,000 gain or an ADC with 16 bit resolution. Can you please confirm?
I have searched for a PGA with 10,000 gain but the highest gain I found is 1,000. Do we have an alternative solution for this application?

Regards,

Danilo 

  • 0
    TI__Genius 17990 points

    Hello Danilo,

    The INA226 has a voltage measurement range of 81.92mV, with an LSB of 2.5µV, so if you use an optimized shunt value to measure 200A, then you would need a shunt resistor of 8.192mV / 200A = 0.4096mΩ. With this shunt, a measurement of 0.01A corresponds to 0.4096mΩ * 0.01A = 0.004096mV, or 4.096µA. Since the INA226 has an LSB of 2.5µV, it has the desired resolution for the mentioned system, with an ideal shunt.  However, that is just the resolution step size, not the accuracy. In order to get more accurate measurements, they would want to use the longest possible conversion time, and possibly do some averaging as well.  Also, it's important to note that the INA226 will not be as accurate at very low currents, due to the voltage offset and input bias current.

    I recommend using the INA238 instead. This has similar accuracy and cost to the INA226, but is newer and has more features. In addition, it will be able to measure very low currents better than the INA226, due to it's low input bias current and voltage offset.

    If they want even better accuracy, then they may want to consider the INA228, which has a 20 bit ADC, instead of the 16 bit that both the INA238 and INA226 have. The INA228 is also one of the newer devices, and has even more features than the INA238.

    All the above devices use I2C communication, if they prefer SPI, then they may want to look at the INA229 and INA239 instead.

  • 0 in reply to Mitch M
    TI__Mastermind 24695 points

    Hi Mitch,

    Thank you very much for your clear answer to this inquiry.

    Regards,

    Danilo