Hey all, I am trying to make a cheap ammeter for my power supply. My original plan was to use 10 series resistors to split a reference voltage from a +5 or +12V regulator. I was also going to place a .5ohm resistor in series with the final output. I planned on comparing the reference voltages with the with voltage across the resistor. - Vr + out ----|\|\|\|----- My problem is that 339 comparators have a single ground for the comparisons, if I were to connect the -Vr to ground, and the +Vr to the comparators V+, with the V- being the reference voltage, the whole thing would be messed up (in terms of difference between voltages). Does anyone know how I could compare the two signals using a common ground? Thanks, John edit: I think it may work if the resistor was instead connected between ground and the black power supply lead. Does anyone know if this would work?