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Can an INA3221 module (Triple-Channel, High-Side Measurement, Shunt and Bus Voltage Monitor with I2C- and SMBUS-Compatible Interface) be used to read the current in a ATX 12/5/3.3 V computer power supply accurately? Or does the common ground cause some issues?

I have not found any information about this by googling.

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    \$\begingroup\$ What do you mean by accurately? \$\endgroup\$
    – Justme
    Commented Dec 25, 2022 at 10:30

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From the lack of details we could also assume you are not using the IC directly, but a manufactured module. If this is the case, additionally to the ground connection, you should be careful with:

  • Some boards have the three power inputs shorted (they measure the current for three loads powered by a single voltage). Certainly not what you want.

  • Some boards use \$10m\Omega\$ shunts and others use \$100m\Omega\$ with thinner PCB traces. Since we don't know your current measurement ranges, this may also represent a relevant voltage drop.

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    \$\begingroup\$ Also many cheap INA3221 modules have far too thin traces to carry the proposed current at all. Some can't handle multiple voltages but only multiple current sinks. Sketch their circuit and understand it. I would nowadays prefer to make my own (after having received scrap via an Ebay-dealer). \$\endgroup\$
    – datenheim
    Commented Dec 25, 2022 at 15:47
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INA3221 measures the high side current so, yes it is suited to used in ATX-like environments.

The main problem I see with ATX is that there are so many different 12V 3.3V and 5V wires that installing one such that it gives useful results may be tricky.

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In the first page of the datasheet there is a picture of how to measure three supply currents that shares a common ground.

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