Multiple INA219 current sensors in one system?

[MathiasVDA]

Hello all,

I have purchased 4 INA219 current sensors and am deploying them to measure current flows in one system. I'm using a seperate Arduino Mega to power and read the current sensor and display the values to an LCD screen. That arduino is connected to a different battery then the circuit I'm trying to sense.

I then placed the current sensors in series with the system to be analysed. In short: I placed a sensor before a buck converter (AZV/5VDC) and after the buck converter. I notice that when i do not use a common ground, that the readings I get from the INA are incorrect. I'm not sure if it's related but the current measurement is about the same for the 12V circuit as for the 5V circuit. But when I short both grounds of the batteries and create a common ground, then I get correct readings.

I know when the readings are (in)correct because I've placed a multimeter in series.

Although I have discovered a solution for the problem, I remain intrigued by the situation because I thought the common ground would not be necessary: the INA219 needs to measure voltage differences and therefor is independent on voltage level (up to the insulating properties offcourse). What am I missing here?

Thanks!

[Franklin97355]

You need a ground to all devices to allow for e return path for the data. The clock is a pulse in reference to ground and the data is also.

[josephchrzempiec]

Hello i have tried four of the INA219 modules. But my question is it possible to do more then Four boards?

[Franklin97355]

You can add a multiplexer to the i2c bus.

[josephchrzempiec]

Hello thank you for that information. But here is my problem. I have up to 14 devices is To many wires going from device to chip device to chip and etc. I'm trying to do like a i2c chain where only two wires and a ground. I'm monitoring voltages cells up to 4.2v and there are 14 of them. I first wanted to use a Lipo fuel gauge or the INA219 current/Voltage sensor.. Because it had a fix address could not put more then 1 on the I2C lines. But this this chip i can do that now. Only problem is i need analog lines and i2c lines or whatnot so many wires. How do i limit all of these wires I'm trying to keep it as small as possible because i already have a lot of wires going to other digital devices??


Joseph

[ImaginaryAxis]

Unfortunately, you cannot get around this issue if you are deadbugging a proof of concept project. If you have 14 current shunt monitors on their own breakout board, analog lines for signals and loads, and grounding, you are simply going to need to be mindful of your wires.

After your proof of concept, it may be miniaturized on a single PCB.

I developed a similar, multi-node project with temperature sensors, and they were all connected via LINBus. TX, RX, and GND were all connected to wires to each node which was in parallel with the bus. It can be a hassle.

[joex2]

In my design, I use 6 INA219 sensors, each monitoring different DC-DC converter power with different power return path (very noisy, Digital, Analog returns)

Arduino circuit and its sensors are powered off of one of the power supplies, 5V (digital).

All 6 power supply returns are eventually tied together at the main DC input.

For the accurate measurement of Voltage and current, what shall I connect the GND pin of each INA219 to? is it okay to connect all 6 sensor GND pins to the digital ground?

Thank you in advance.