Com-Power near field probes have nice, compact nylon tips that allows for access into small circuitry and narrow down location of source interference to within the centimeter. The EMC Shop stocks these Com-Power near-field probe sets for rental or sale. Near-field magnetic (H-field) and electric (E-field) probes let you "sniff" around the circuits, cables, and enclosures to find the source. H-field probes use a conductive loop to detect magnetic fields produced by clock signals, serial data streams, control signals, and switching power supplies. You can often uncover the source of EMI emissions with near-field probes.