Whitepaper
Applications of HF Current Probes
This technical article explores advanced uses of high-frequency RF current probes beyond basic current measurement, using the Com-Power CLCE-400 as a reference tool throughout. It opens by explaining transfer impedance — the ratio of probe output voltage to current in the conductor under test — and how to use it to calculate common mode (CM) current levels. Three main applications are then presented. The first demonstrates how to predict radiated emissions pass/fail outcomes by measuring CM currents on cables and calculating the expected electric field using a standard formula. The second shows how to isolate common mode from differential mode conducted emissions using a current probe, enabling more targeted filter design decisions. The third describes a three-step bench-level troubleshooting process for radiated emissions: near-field probing to identify noise sources, current probe measurements on cables to quantify and locate dominant harmonics, and close-spaced antenna measurements to confirm actual radiation. The article concludes with five practical troubleshooting tips covering probe positioning techniques, dual-probe comparisons, and coupling type identification.