The increasing share of power electronic (PE) devices in public energy networks has caused harmonic instabilities. A harmonic instability implies an interaction of the device control with the network impedance that leads to an unwanted shut down of the PE device. To analyze and predict the PE device behavior, different study approaches have been developed. While white-box approaches are not always applicable since the parameters of the devices are not always disclosed, black-box models can be generated based on measurements and used for the stability analysis. However, the measurements require expensive and accurate grid-simulators. The aim of this paper is to provide a measurement-based black-box method to analyze the harmonic stability of single-phase PE devices for low power applications in LV networks without deriving PE device models. Next to air coils as test stand impedances, a simple voltage source that generates a sinusoidal voltage at power frequency is sufficient for the proposed method. The method is demonstrated on a commercially available single-phase photovoltaic inverter and validated by the respective background theory.