@ instructables.com writes:
This is an accurate milliohm meter with a maximum resolution of 0.1mOhm. The design is very simple, the whole assembly can be built in a couple of hours once all the parts are gathered. It is based on a precision current sink and a high-resolution ADC controlled by an Arduino Nano V3. It uses a Kelvin connection with the resistor under test to exclude the resistance of test leads from the measurements. It can be very useful for measuring small resistors and the resistance of PCB traces, motor coils, inductance coils, transformer coils, or calculate the length of wires.
Arduino Milliohm Meter – [Link]