A system includes a first powered apparatus having a first analog signal with a fundamental frequency; and a second apparatus providing load diagnostics or power quality assessment of the first apparatus from a second digital signal. The second apparatus includes an input of the first analog signal, an output of the second digital signal, a processor, an adaptive filter executed by the processor, a digital-to-analog converter, and an analog-to-digital converter. The adaptive filter routine outputs a third digital signal as a function of the second digital signal and plural adaptive weights. The digital-to-analog converter inputs the third digital signal and outputs a fourth analog signal representative of an estimate of a fundamental frequency component of the first analog signal. The analog-to-digital converter inputs a difference between the first and fourth analog signals, and outputs the second digital signal representative of the first analog signal with the fundamental frequency component removed.