A portable voltage detector (100) comprises a housing (106), a sensor circuit accommodated in the housing (106) for detecting electric fields (501) within a detection range of the portable voltage detector (100), an evaluation unit accommodated in the housing (106) for evaluating the detected electric fields, the evaluation unit being connected to the sensor circuit. A warning device (104) connected to the evaluation unit is set up to output a warning signal if the strength of an electric field (501) detected by the sensor circuit reaches or exceeds a warning threshold. A wireless communication interface of the portable voltage detector (100) connected to the evaluation unit is configured to receive a setting signal to determine the warning threshold. A voltage source connected to the sensor circuit and the communication interface is configured to be charged by means of a unit for inductive charging.

Improved probing of devices under test that have an impedance mismatch to the test equipment is provided. The probes are connected to the test equipment via a flexible circuit, and the impedance matching is done using lumped elements in the flexible circuit. Such lumped elements can be integral to transmission lines in the flexible circuit.