A portable measurement device, comprising: an elongated body (102, 202) with a distal end and a proximal end; a stationary portion (106, 206) fixedly mounted to the distal end, and a movable jaw (108, 208) movably mounted to the distal end and movable between a closed position and an open position, wherein a closed loop formed in the closed position is configured to generate a sensing current, and in the open position the movable jaw (108, 208) and the stationary portion (106, 206) define a gap allowing a wire under test to pass therethrough into the loop between the movable jaw and the stationary portion; a switch configured to drive the movable jaw (108, 208) to move between the closed position and the open position; and a measurement circuit disposed within the elongated body (102, 202) and electrically coupled to the stationary portion (106, 206) and the movable jaw (108, 208), the measurement circuit being configured to receive and measure the sensing current, wherein the movable jaw (108, 208) is of a semi-circular shape and is slidable along a lengthwise direction of the elongated body (102, 202) to move between the open position and the closed position; in the open position, the movable jaw (108, 208) is slid in the lengthwise direction away from the elongated body (102, 202), characterized in that in the closed position, the movable jaw (108, 208) and the stationary portion (106, 206) form the closed loop with an inner diameter of less than or equal to 10 mm; and the stationary portion (106, 206) has at its distal end an extension arm which forms a portion of the closed loop, wherein the extension arm is movable relative to the movable jaw (108, 208) for opening or closing the closed loop. an elongated body (102, 202) with a distal end and a proximal end; a stationary portion (106, 206) fixedly mounted to the distal end, and a movable jaw (108, 208) movably mounted to the distal end and movable between a closed position and an open position, wherein a closed loop formed in the closed position is configured to generate a sensing current, and in the open position the movable jaw (108, 208) and the stationary portion (106, 206) define a gap allowing a wire under test to pass therethrough into the loop between the movable jaw and the stationary portion; a switch configured to drive the movable jaw (108, 208) to move between the closed position and the open position; and a measurement circuit disposed within the elongated body (102, 202) and electrically coupled to the stationary portion (106, 206) and the movable jaw (108, 208), the measurement circuit being configured to receive and measure the sensing current, wherein the movable jaw (108, 208) is of a semi-circular shape and is slidable along a lengthwise direction of the elongated body (102, 202) to move between the open position and the closed position; in the open position, the movable jaw (108, 208) is slid in the lengthwise direction away from the elongated body (102, 202), characterized in that in the closed position, the movable jaw (108, 208) and the stationary portion (106, 206) form the closed loop with an inner diameter of less than or equal to 10 mm; and the stationary portion (106, 206) has at its distal end an extension arm which forms a portion of the closed loop, wherein the extension arm is movable relative to the movable jaw (108, 208) for opening or closing the closed loop.