INA226 , INA228 red module

[oduled]

Hello, Could you add connection diagram for the red module with 0.002ohm shunt resistor?
Did you try using same module with INA228 ?

[wollewald]

Hi @oduled , I have added a circuit diagram for the red module. There are different options: you can apply it on the high side, on low side, and you can include the shunt vor the bus voltage and power measurements or not.
Important is to not use the small In-/In+ connectors, but the bigger connectors which are labelled as "Current + / -". For reasons I don't understand there are 4.7 ohm resistors between In+ and the shunt and between In- and the shunt. To me this makes no sense.

I have not seen an INA228 module anywhere. Have you found it somewhere? If yes, I would be interested in a link.

I was thinking about including other INAxxx current and power sensors but there are so many:
https://www.ti.com/amplifier-circuit/current-sense/digital-power-monitors/products.html
Maybe I will have a closer look into the ones which have three or four channels.

I hope this answers your questions.

[wollewald]

A short addition to my comment: The 4.7 ohm resistors do make sense. It seems that the developers of the modules have followed the recommendations in the datasheet and added a filter:

But if you let your load current flow through the IN+/IN- connectors on the module, the INA226 measures the voltage drop over the two 4.7 ohm and the shunt resistor - and that makes no sense and is very confusing.

[oduled]

Hi,
Thanks that you update library and schematic diagram
I bought INA228 from AliExpress ,It's with same INA226 PCB, chip pinout is the same.
What I need to do for using it in fast mode(400kHz) or High speed mode 2.94MHz?
What is the short amplitude pulse that I can measure with it?

[wollewald]

Hi @oduled , the INA226 and the INA228 may have the same pinout but internally they are very different. For example: the INA228 has 20 registers, the INA 226 has only 10. The INA228 is a 20 bit device, The INA226 is a 20 bit device. If I planned to write a library for the INA228, it would be a separate one. It's not much code which could be recycled.

I found two other libraries on Github which you could try:
https://github.com/adafruit/Adafruit_INA228
https://github.com/RobTillaart/INA228

Meanwhile I have also found IN228 based modules. I will order some and test the libraries. Depending on the result I might write an own library, but even if I decide to do this, it will take time.

[JoeggiCH]

Hi "Wolle" :-)

Thanks for the great library. It helps me a lot in my first Arduino project here 👍 👍
I am also using the "red module".

You wrote

It seems that the developers of the modules have followed the recommendations in the datasheet and added a filter

Yes, the 4.7 ohm resistors are the RFILTER resistors in the circuit in 6.4.2 of the INA226 datasheet.

But if you let your load current flow through the IN+/IN- connectors on the module, the INA226 measures the voltage drop over the two 4.7 ohm and the shunt resistor - and that makes no sense and is very confusing.

If we want to use the shunt and the filter on the module, the load must always be connected to Current+ or Current- of the module.

The copper pads IN+ and IN- on the module are only relevant, if we want to measure the signal to the INA226 or if we want to use the module with shunts/filters other than those on the module.

If we connect the load to Current+ / Current- of the module, the load current is divided , i.e. the vast majority of the load current will flow via the shunt resistor and only very little current is via RFILTER resistors and the INA226 pins. In the case of the red module the load current is divided between

• path 1 - via the shunt with 0.002ohm
• path 2 - via the "upper" RFILTER 4.7 ohm, the INA226 pins, the "lower" RFILTER 4.7 ohm

Because the resistance on path 1 is much smaller than on path 2, the current on path 1 is much higher than on path 2.

Again, from the datasheet

The INA226 device performs two measurements on the power-supply bus of interest. The voltage developed from the load current that flows through a shunt resistor creates a shunt voltage that is measured at the IN+ and IN– pins.

The INA226 measures the shunt voltage and calculates the load current and power from that. The INA226 is designed to consume very little current. The datasheet section 5.5 mentions the "input bias current" with a value of 0.1nA. I understand this is the current we would measure on path2!