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INA197 - Current Measurement Accuracy

Kawai
Guru 19775 points
Other Parts Discussed in Thread: INA197

Hello Team,

Could you please tell me how to calculate the monitoring accuracy using INA197 ? I have a few question about this.

[Q1]
INA197 offset voltage MAX is 3mV. As the gain is 50V/V, does this mean that input error would be 150mV ?

[Q2]
Could you please tell me how to calculate the monitoring accuracy for INA197 ?

I believe below are the error factor.

- Input offset voltage (MAX)
- Gain Error (MAX)
- Common Mode Rejection (MIN)
- Power Supply Rejection (MIN)
- Input Offset Current (MAX)
- Shunt Resistor Tolerance (MAX)

If there is an app note which describes this, could you share us the material ?

Best Regards,
Kawai

  • 0
    TI__Intellectual 2480 points

    Hello Kawai,

    1. Correct. The input offset voltage is 3mV outside of room temperature operation, and this means that the output offset would be 150mV for a gain of 50V/V. It is important to note that this 150mV is output offset, not input error.

    2. If you look on page 17 of the INA197 datasheet, you will see a section which goes into detail of the effects of Vsense, Common Mode voltage, offset voltage, and gain error in a comprehensive manner. You will see that depending on the system conditions, different graphs will be referenced that will help you, such as Figure 6 which shows the effect of common mode voltage on output error.

    Regards,
    -Kareem Moulana

  • 0 in reply to Kareem Moulana
    TI__Expert 4595 points

    Hello Kawai,

    Also the Electrical Characteristic table in the INA197 datasheet has a Max Total Output Error spec of about 2.2% for Vsense= 100 mV (only including Vos and Gain error). There are additional errors like shunt resistor tolerances that contribute to the total error. Please take a look at the below table from another datasheet for an error calculation example (Note that RVRR error is not applicable for this device).