EMC Hire provide a range of Conducted Emissions Testing Equipment. There are three subsections under the general title Electromagnetic transducers-Conducted. The first subsection Current Probes and Clamps deals with conducted emissions as measured by current probes and clamps. Most of the current probes are hinged & will open & then clamp around the cable to be measured with a small locking clip.
Fundamentally, a current clamp becomes the secondary winding of an effective current transformer whose primary is the cable or conductor to be measured.