A device (10) for measuring an impedance (Z 2 ) between first and second nodes (22, 24) in an electrical circuit (18) without removing components includes at least one current source (62 and/or 66) to provide first and second currents or current signals (i 0 , i 1 ) of known values. First and second probes (30, 34) contact the respective first and second nodes to apply the first and second currents. A third common probe (46) contacts the circuit at a common node (50) that experiences the same current flow as between the first and second nodes. At least one voltage meter (70 and/or 74) measures voltages (V 00 , V 01 , V 11 and V 10 ) corresponding to the first and second currents. A processor (100) calculates the impedance based on the known values of the currents, and the measured values of the voltages.