Would like to have a simple milliohmeter for car wiring checking. Precision is not important, it's not about 3 vs 4 mΩ, it's about 3 vs 30 vs 300 mΩ.
Simple idea is a 1A floating current source (2 alkaline AA batteries and a very basic circuit) and using an ordinary multimeter to measure mΩ as mV in a 4-Wire connection.
An important point is that the circuit survives most possible abuses, specially being connected directly at +/- 12V on the RX terminals. I think it will survive having -12V at Q2 collector but I'm not really sure.
Will have to see if two AA are enough or it needs a third to go 4.5 V.
Do you think this would work? What would you change while keeping it cheap and simple?