Tektronix probe 119-4146-00

Tektronix 119-4146-00 Near-Field Probe Kit is designed as a versatile tool to assist in diagnosing radiated emissions across a test frequency range from below 100 kHz to over 1 GHz.

The probe kit consists of three (3) magnetic field probes, two (2) electric field probes, a 20 cm extension handle, and a custom carrying case.

Three magnetic field probes are electrically small (i.e., loops with different sensitivities and resonant frequencies above 1 GHz). These loops are wound inside balanced Faraday shielding, which reduces their response to electric fields to negligible levels. Each progressively larger loop increases sensitivity (independent of frequency) by about 12-155 dB. Probes with reduced sensitivity may help more accurately isolate emission sources.

Two electric field probes consist of a ball and a short-circuited line. Each probe mainly responds to the electric field component while suppressing the magnetic field component.

When making before-and-after measurements to determine the effectiveness of attempted EMI solutions, care should be taken to ensure measurements are repeatable. The most important factor is the distance between the probe and the device under test. Even small changes in this spacing can result in significant amplitude variations. Due to capacitive coupling with external objects (such as chassis, human body, large metal objects, etc.), E-field probes are also susceptible to measurement variations. H-field probes do not experience this effect.

The response of E-field probes is essentially omnidirectional. H-field probes have a figure-eight response, typical of a dipole. The primary pickup direction is the side of the loop, with sharp nulls in the plane of the loop.

Probe selection depends on the type of signal observed, signal strength, and the physical size of the area to be investigated. Comparing the responses of H- and E-field probes will give users an idea of the relative sizes of E- and H-fields for each component, providing clues for addressing emissions issues. Larger probes offer higher sensitivity, while smaller probes can more precisely locate emission sources.

The kit weighs 4.6 lb (2.1 kg) including the probes, and the case measures 11 inches (28 cm) x 12.75 inches (32.4 cm) x 4.75 inches (12.1 cm).