KC R20 Near Field Probe kit includes 3 different size passive magnetic field probe, and 1 passive E-field probe. It has flat frequency response in the 30MHz to 3GHz, used to measure the magnetic field and E-field during the developmental stages.
The following picture is the old version, the handle is white, as a function display. The current versions are all black handles.
They are also sensitive at low frequencies. The probe diameter of three probes are 20 mm, 10 mm, and 5 mm. The larger probe has high sensitivity, but low directional resolution. Instead, smaller probes have low sensitivity but high directional resolution.
Usually, we use the large one to detect where the interfering source is roughly located, and then use a smaller probe to narrow the search range, and identify the source of the interfering magnetic field in the electronic module step-by-step.
Measure the magnetic field
Measure the electric field