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INA226EVM: INA226EVM

Eric Cui13
Intellectual 920 points

Part Number: INA226EVM
Other Parts Discussed in Thread: INA226,

Hi,

  The configured detection time is 1.1 ms. The length of the inspection line is 300mm x 2.

1. Shunt resistance is 0.000375 ohm.

2. Multimeter is fluke's high-precision multimeter, in the ammeter is fluke clamp ammeter

How to adjust can improve the detection accuracy?

  INA226  Voltage (mV) high-precision multimeter
(mV)		 Voltage error INA226 current
(A)		  Ammeter
(A)		 Charger number
(A)
充电 -3.738 -3.816 -0.078 9.96 9.9 10.01
-18.22 -18.58 -0.36 48.58 49.7 50.02
-36.57 -37.262 -0.692 97.55 99.8 99.99
-55.44 -56.26 -0.82 147.9 150.3 149.98
-74.44 -75.53 -1.09 198.6 200.6 200
-74.67 -75.62 -0.95 199 200.6 200
放电 3.52 3.557 0.037 9.382 9.8 9.98
10.73 10.96 0.23 28.63 29.8 29.96
18 18.35 0.35 47.97 49.7 49.99
25.3 25.77 0.47 67.5 69.7 70
34.48 35.07 0.59 91.96 94.6 95

Thank you.

  • 0
    Guru 140200 points
    Hi Eric,

    what shunt do you use? Does it have 4 terminals?

    Kai
  • 0
    TI__Mastermind 26335 points

    Hello Eric,

    Thank you for considering to use the INA226 in your system.  All current sense monitors will have some inherent sources of error.  However, we expect for the error to always decrease with increased current or increase voltage drop across the shunt resistor.  From your top measurement, I presume your were measuring roughly (-.0003738V - Vos)/.000375ohm = -.0003728V/.000375ohm=-9.94133A.  I suspect Based off that, it seems that you have roughly 7.85uohms between the shunt terminals and your multimeter probes.  Since your shunt resistance is so small, shunt layout, shunt choice, and probe placement are critical.  The INA226EVM may not actually provide the best layout for such a small resistance, as the shunt should be placed very close to the INA226 with matched trace lengths leading from the shunt to the INA226.  Also, as Kai pointed out, this should be a four terminal resistor with Kelvin connections.  A footprint for such a resistor is not on that EVM.  Also, I would stress that the resistor tolerance is important.  On that note, do not use a copper trace for your shunt.  Copper resistance may vary more with temperature than the resistance of a proper shunt.  As for your probes, shorter twisted pairs are always better.  Fine tipped probes would also be advised to give you the option of probing right on the device pins.

    As for probe place placement, below is a diagram that possibly illustrates your issue.  As you probe further from the device you will see a larger differential on your precision multimeter.