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INA220: help needed in error correction

Part Number: INA220
Other Parts Discussed in Thread: INA3221, INA231, INA230, INA233, INA226, INA260

Hi Team, 

Customer is using the INA220 for monitoring the current across shunt in the battery application.

They are sampling the current every 2ms and computing the RMS over a time period of 10s. Customer see an abrupt value on one sample randomly, which is affecting the computation of the RMS and the subsequent averaging. What could be the possible reason for this abrupt value and any suggestion to mitigate it.

 

Any sample reference acquisition flow is recommended for the device?

 

The typical measured values are in the range of -0.32 to +0.32. The sudden abrupt reading is around 23.04. 

  • Hey Naveen,

    I think this might have something to do with reading the data during the register update which can be a problem for the INA220 (newer devices will not have this problem). The best practice would be to operate the part in triggered mode (section 8.3.1). This is accomplished by writing to the configuration register to trigger a single conversion. Once the conversion is complete and registers updated, the conversion ready bit (CNVR) will go high. Host can retrieve current data once the single conversion has been completed and then repeat this process every ~2ms, although maybe they want to send a trigger every 1ms if they choose a 1ms conversion time so that a sample is gathered every 2ms.

    Best,

    Peter

  • INA220AIDGST                   

    We are currently using this device for this application. It is mentioned newer devices will not have problem. Is it any other device variant from TI ? .Kindly specify in detail

  • Hey Shekhar,

    Of course. My apologies for not leaving alternatives. The following TI digital current sense amplifiers should the solve the aforementioned issue: INA226, INA230, INA231, INA233, INA260, and INA3221.

    I would recommend first confirming that the problem you are seeing with the measurements is in fact the issue I am bringing up. You can confirm this by reading all measurements with the trigger mode sequence I explained in my first post. If the problem goes away, then you could chose from one of the alternative parts above as a fix.

    Hope this helps.

    Best,

    Peter

  • Hi ,

    We are facing another problem while measuring the current for detection of direction of current.. Our electronics is connected to a battery where the  battery will be charged & discharged . Using INA 220 how the values of INA can be used for detecting the change in direction. 

  • Hey Shekhar,

    You will use the sign bit (bit 15) of the shunt voltage register to determine the direction of the current. See section 8.6.3.1 of the datasheet.

    Remember that Vshunt = (V_IN+) - (V_IN-). So if IN+ is closer to the battery, then negative Vshunt means the current is flowing into the batter for charging.

    Hope this helps.

    Best, 

    Peter