Subharmonic frequencies produced in non-linear systems

IN BRIDGE measurements, harmonics, due to a nonlinear load being measured or due to the power supply may fail to be balanced at the same time the fundamental is balanced. This impresses on the detecting system a wave containing a large proportion of harmonics, or, at true fundamental balance, harmonics without fundamental component. The detecting system contains magnetic materials and may include a vacuum tube amplifier. Different observers have found errors which they traced to the apparent conversion of part of the harmonics into a fundamental component.