A device (10) for measuring an impedance (Z2) 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 (i0, i1) 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 (V00, V01, V11 and V10) 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.