Voltage/Amperage sampling to SD Card

Thread Starter


Joined Aug 22, 2011
Hello everyone.

New member here, sorry if this has been covered, but I'm guessing its a pretty unique situation.

what I would like to do is design a circuit to test battery chargers at my company. I would like this circuit to detect charge current, up to 30A, and voltage. I would like this data to be recorded, and stored on an SD card. I had thought of using an arduino for the storage and logic functions, but I am not sure of the best way to design the current/voltage sensing circuit.

Thanks for the help, in advance.


Joined Sep 9, 2010
The two common ways of sensing current are to use a Hall effect sensor (non invasive) or pass the current through a high power, low ohms shunt resistor and measure the voltage developed across that resistor.

You might consider a data acquisition device such as the LabJack for measuring and recording your data. You could log the data directly into Excel for instance, for easy analysis.


Joined Jul 17, 2007
Here's a link to an SD library for the Arduino:

For detecting amperage, you'll need either a current shunt (basically a very low-value resistor, frequently made from round brass stock) and you will need to use an ADC to measure the voltage drop across the shunt.

You will also need to use a voltage divider from the charger positive to measure the charge voltage using an ADC.

You'll also need to write the code to do these things, and write the data to the SD card using the SD library.