A Positive Ground System Works in the following ways; Adjust the meter to its forbearance setting and measure the resistance of test points in the circuit. Do this step before you power on the circuit. Fix the multimeter to the power scale. Align the circuit to measure current at your selected test points. Current measurements require you to replace a section of the circuit with a current path through the multimeter. Configure the meter to measure current and then observe the polarity of the current input leads.