DC current sensor - 26V, 3.2A max - I2C

Measure DC current with the INA219 breakout

This breakout will solve all your power monitoring problems. Rather than messing around with two multimeters, you can use the INA219B circuit fitted on this breakout board. Il will help tp measure both the high-side voltage and the current drawn with 1% accuracy. All via an I2C interface..

This breakout is now fitted with Qwiic / StemmaQt connector

High Side and Low Side measurement

A quick summary:

• "High Side" measurement = measure on the "+" of the load... so on the "+" side of the supply.
• "Low Side" measurement = measure on the "-" of the load... so on the ground side.

Most current measuring devices works on the low voltage side of the circuit (called "Low Side Current Sensing"). This means that if you want to involve the power supply in the measurement process, you must place a resistor between the ground of your load (e.g. the "-" pole of a motor or an electronic device) and the real ground of the circuit. Therefore, the potential difference across this resistor varies depending on the current flowing through it (the higher is the current, the higher will be the voltage across the resistor, even if we are only talking about a few millivolts).
This means that the "-" terminal of your load is no longer at TRUE ground (at 0 volts) but at a virtual ground located a few millivolts above the REAL ground... this virtual ground also varies slightly depending on the current flowing through the load (and the measuring resistance).

The "low side" measurement that is done on the "-" terminal of the load can cause problems when the load have electronics circuitry. electronic assemblies tend not to appreciate grounds with a voltage reference that varies!

NB: The "Low-side" measurement has a definite advantage for the sensor. The measuring electronics do not have to withstand high voltages (from 1 to a few volts is more than enough).

This breakout is made for High-Side measurement

The INA219 chip is smarter - it is capable of measuring "High Side" current (on the "+" side of the load), up to +26V DC, even if the breakout it is powered with a voltage of 3 or 5V.
Since it made "high side" measurement, it can also measure the supply voltage! Great for monitoring the life cycle of a battery or solar panel.

A precision amplifier measures the voltage across a 0.1 ohm resistor fitted on the breakout (1% sensing resistor). Since the maximum input difference of the amplifier is ±320mV, that implies that a maximum current of +/-3.2 Amps can be measured. The INA219 have an internal 12-bit ADC converter, the resolution over the +/-3.2A range is then 0.8mA!
With an internal gain configured at a minimum of div8 (divided by 8), the maximum current is +/400mA with, this time, a resolution of 0.1mA.

Experienced user could remove the 0.1 Ohm sensor resistor and replace it with their own resistor. With a 0.01 ohm, it is possible to measure a current up to 32 Amps with 8mA resolution.

How to wire?

This breakout includes a 2.54mm pin header and a 3.5mm terminal block that you can optionally solder onto the board. The terminal block will be useful for connecting the load and the pin header would be welcome to plug the breakout on breadboard. The Qwiic/StemmaQt connectors will be welcome for quick wiring on a Qwiic / StemmaQt capable plateform.

A simple usage:

• Connect the sensor to 3 to 5V DC logic  supply
• Connect the I2C signals to your microcontroler.
• Connect the High Power Supply to the VIN+ pin.
• Connect the VIN- pin to the load (the other side of the load have to be connected to the ground).

Technical details

• Current reading resistance: 0.1 ohm 1% 2W
• Maximum high side voltage: up to +26V
• Maximum current measurement: up to 3.2A (resolution of 0.8mA).
• Size: 25.6mm x 20.4mm  (height: 4.7mm)
• I2C addresses: 0x40, 0x41, 0x44, 0x45 (selectable)
• INA219 datasheet