The absorbing clamps also known as ferrite clamps are used for measuring disturbance power on power input lines as well as other auxiliary I/O lines.
Absorbing Clamps to measure EMI Emissions according to CISPR 13 [EN 55013], CISPR 14 [EN 55014] and CISPR 32 [EN 55032] The absorbing clamps also known as ferrite clamps are used for measuring disturbance power on power input lines as well as other auxiliary I/O lines. The absorbing clamp measurement method (ACMM) is described in Clause 7 of CISPR 16-2-2. The CLA-050 and CLA-150 consist of a broadband current transformer (30 MHz to 1 GHz) and two sets of ferrite rings.
The line(s) under test are routed through the current transformer and one of the set of ferrite rings. The ferrite rings act as a broadband RF power absorber and isolates the current transformer from disturbances on the mains and establishes asymmetric (common-mode) impedance. Each of these ferrites are split into two halves, with one half mounted in the absorbing clamp base, and the other half mounted in the hinged top cover.
When the clamp is open, the line(s) under test are easily laid into place inside the bottom halves of the ferrites. When the clamp is closed, the two halves meet, forming a ring around the line(s) under test. The coaxial line connecting the current transformer to the clamp