The F-12 measures currents on 400 Hz powerlines. This probe has a usable frequency range of 10 Hz to 3 MHz with a transfer impedance from 0.33W (± 2 dB) 500 Hz to 3 MHz. Primary power currents of 350 amps DC to 400 Hz will not alter the transfer impedance. The probe can be used to measure conducted emissions and investigate low level harmonics.