Current / Voltage

April 30, 2019

Some info about current / voltage sensors

Current & Voltage Sensors

These are Integrated sensors that detect both the current, and the voltage (then, following Ohm’s law, the power) of a circuit.

The most common method for measuring currents in electronic circuits is to place low-value sense resistors in series with the load and measure the voltage drop across them.

INA219 High Side DC Current Sensor

This breakout board allows for power monitoring, including both a High side voltage and DC current draw sensor over I2C.

High-side and low-side current sensing refers to the placement of the current-sense resistor:

  • High Side - between the positive supply and the load (whatever is being driven by the circuit);
  • Low Side - between the load and ground.


  1. Ground;
  2. Vcc, power with 5V;
  3. SDA data pin;
  4. SCL clock pin;
  5. Vin- terminal (if you want to use another current sensor);
  6. Vin+ terminal (if you want to use another current sensor);
  7. Vin- of INA219 DC current sensor;
  8. Vin+ of INA219 DC current sensor;

Technical Details

  • 1% precision;
  • High Side measurement, up to +26V DC;
  • Powered with 3-5V;
  • Uses precision amplifier to measure voltage across 0.1Ω , 1% sense resistor;
  • Can measure up to ±3.2A (since internal amplifier has maximum input resolution of ±320mV);
  • Internal 12bit ADC( Analog to Digital converter);
  • Resolution of 0.8mA at ±3.2A range.

This breakout requires the use of the library Adafruit INA219.

Now lets see a list of terms for the sensor:

  • Bus voltage - voltage between GND and V-, total voltage seen by circuit under test. (supply voltage - shunt voltage);
  • Shunt voltage - voltage between V- and V+, voltage drop across the shunt resistor;


Power sensor of a simple Circuit

We’ll be making use of all the basic functionalities of this breakout to do some simple measurements of a basic circuit!



Now, let’s see what our console should look like:

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