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INA226-Q1: has a large sampling error

SUN xuran
Prodigy 40 points
Part Number: INA226-Q1
Other Parts Discussed in Thread: INA226

Tool/software:

We use INA226 to measure the current output of a half-bridge, directly reading the shunt voltage, i.e. the Shunt Voltage Register register, with a shunt resistor of 1m ohm. We also use an oscilloscope to measure the output current, but we find that no matter how we adjust the conversion time and the number of samples, the Shunt Voltage is always smaller than what the oscilloscope measures. Why is this? How can we configure it?

For example，We read the shunt voltage of INA226 through the serial port as 0.006182V (Rshunt=1mΩ)，but at this time the output mean current read by the oscilloscope is 6.964A

  • 0
    TI__Mastermind 26915 points

    Hello Sun,

    Here are a couple of ideas of why you may be seeing a difference. It could even be a combination of these.

    • It looks like the minimum measurement you are getting from the scope is 5.061A, so you could try to increase the averaging and conversion time of the INA226 to see if the value matches your average more closely. 
    • If the scope and INA are measuring from different locations, the voltage could be different due to variation in shunt or input filter resistor tolerances (or other layout related factors). I recommend using a multimeter to measure the voltage right at the input pins of the INA226 to confirm that the voltage you are reading with the multimeter is the same as the INA226 is reading. 

    Regards,

    Mitch