Verifying MIL-STD-461G CS101 using frequency domain measurements on an oscilloscope

Conducted susceptibility measurements such as MIL-STD-461G CS101 require the insertion of an interfering signal on the power rails of an equipment under test (EUT) and verifying proper operation. The interfering signal includes a range of frequencies and amplitudes as required by the standard. The level of the interfering signal at each frequency must be verified using either an oscilloscope or a test receiver. The latter instrument is used to verify the signal in the frequency domain while the former is used to verify the signal in the time domain. This paper investigates the benefits of using an oscilloscope to verify the signal in the frequency domain using the FFT function found on most oscilloscopes. It will be shown that this method is more reliable and accurate compared with time domain methods and more convenient than receiver measurements while having the ability to safely measure ungrounded power signals using a high voltage differential probe.