different from the contact resistance of the second contact according to an embodiment of the disclosure the power connection terminals 135 a and 135 b the internal circuit 131 the paths path 1 and path 2 and the voltage regulator 140 form a feedback loop during testing the feedback loop is configured to compensate for variation such as the contact resistance variation temperature variation and the like and thus to keep the voltage v u2032 of the power supply within the dut 130 to be substantially the same for different duts 130 or for retests during testing in an example the voltage regulator 140 outputs the power supply having the voltage v to the path path 1 the path path 1 is configured to deliver the power supply to the power connection terminal 135 a the path path 1 has a voltage drop that varies for a different dut 130 or retest due to the variation of the contact resistance for example thus the voltage v u2032 on the power connection terminal 135 a is different from the voltage v output to the path path 1 further the voltage v u2033 on the power connection terminal 135 b is substantially the same.