INA219 Voltage measurements meaning

Question

I have a battery holder, 3 x 1.5V AA, connected to a resistor (100 Ohm or close), LED and Adafruit INA219 breakout board.

The bus voltage reading from the INA219 reports 1.0V. Where does this number come from? The voltage measured at LED tips is 2 The voltage measured at the tips resistor is ~2.6V

Shouldn't the bus voltage be 4.5V?

The INA219 Breakout board Vcc and GND are connected to the ESP32 5V and GND respectively.

If I connect Vcc to the 3.3V the bus voltage shows 0.8.

(Removed the part related to Shunt Voltage since they are milli-Volts)

^{simulate this circuit – Schematic created using CircuitLab}

  if (ina219.begin())
  {
    ina219.setCalibration_16V_400mA();
    Serial.printf("current (mA), Voltage (V): %f %f\n",
    ina219.getCurrent_mA(), ina219.getBusVoltage_V());
  }

output:

 current (mA), Voltage (V): 25.700001 1.012000

Answer 1

According to the "instructions" for your break-out board, one should:

• Power the sensor itself with 3 to 5VDC
• connect the two I2C pins up to your microcontroller.
• connect your target power supply to VIN+
• and the load to ground to VIN-

There are similar instructions here

• Connect V+ to the positive terminal of the power supply for the circuit under test.
• Connect V- to the positive terminal or lead of the load. This puts the sense resistor in-line with the circuit.
• Finally, connect a wire from the negative terminal of the power supply to GND. This allows the sensor to measure the load voltage as well as the load current.

If your schematic is correct, you do not appear to have done this.

1. VIN+ is NOT connected to the target power supply in your schematic
2. the load is NOT connected to VIN- and ground.

If I understand correctly, your circuit should look something like this:

^{simulate this circuit – Schematic created using CircuitLab}