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INA219: INA219 current accuracy

Betty Guo
Expert 7300 points
Part Number: INA219

Hi team,

customer use INA219 measure current, find the have 50~60 mA current error.

test condition as below:

1. bus voltage is 12V; current is 1A; Rshunt =1mA set Curretn _LSB =1mA, reg05=0x1000, reg00 is default.

read current register data and get the current is 1.045A.

2. Change current from 500mA to 2A, always have 50mA gap with actural current.

the quesitons is:

1. does this is normal for INA219 current accuracy?

2. how to redruce the measurement gap. 

thanks.

  • 0
    TI__Mastermind 26660 points

    Hello Betty,

    Is this using the A or B version? What is the internal gain (PGA) set to? This is set in the configuration register (00h). I believe the problem is the shunt resistor and measured current are both relatively small (Vshunt = 0.5mV to 2mV). Even with the lowest offset (INA219B with PGA = /1) set to 50uV, this will translate into a current offset measured by the amplifier of 50uV/1mΩ = 50mA.

    There is also an error in the calibration calculation. Cal = 0.04096/(1mA*1mΩ) = 40,960 dec = 0xA000). You have it listed as 0x1000.

    Please confirm the calibration value and set the device to its lowest gain of PGA=/1 to get the lowest offset. Offset error can always be fixed by increasing shunt resistor or performing an offset calibration. To perform the calibration, take a measurement at 0-A of current and store that value in memory and set it as the 0-A point.

    Hope this helps.

    Best,

    Peter