top of page # Triaxial vector E-field probe How to measure the three components of the E-field vector within a small enclosure? For that purpose, Kapteos introduces a breakthrough with a triaxial vector electric field probe. Such probe allows to measure sequentially the three E-field components while staying in same position and direction. To switch from Ex to Ey component, and then from Ey to Ez component, the probe simply needs to be rotated 120°.

The three components being measured with the same probe in the same position,

• the 3 E-field components are thus assessed with the same antenna factor,

• the Specific Absorption Rate (SAR) can be precisely assessed within an ultra small voxel < 1 mm³,

• the “bio” line triaxial vector electric field probe is perfectly adapted for measurements inside liquid phantoms for SAR measurement & MRI implant safety assessment,

• the “air” line triaxial vector electric field probe constitutes the perfect probe for time-domain measurements of the 3 components of E-field vector in atmospheric pressure plasma jet.

## How does a triaxial vector electric field probe works? Kapteos new triaxial vector electric field probe is based on an electric field probe presenting a sensitivity axis forming an angle of 54.74° with the probe axis. Let us consider an initial probe direction so that its sensitivity axis is aligned with the Cartesian referential X axis (θ = 0°). As seen on the adjacent animation, by simply rotating the probe around its own axis, its sensitivity axis will coincide with Y axis for θ = 120° and then with Z axis for θ = 240°. If we consider also that the E-field vector is perfectly aligned with the X axis, then it is easy to calculate the probe response with respect to angle θ. This latter response, expressed in dB, is represented as the thick red curve on the animation.

## Checking the probe response to 3 electric fields orthogonal each other

A specific setup has been designed to check the orientation of the sensitivity axis of the triaxial vector electric field probe. With this setup, an E field can be applied either along x axis (called Ex and shown in red on the picture), y axis or z axis. The triaxial vector electric field probe is positioned at the center of the setup (not represented on the picture) and the setup is rotated thanks to a motorized rotation stage.

The measured response (dots) of the triaxial vector electric field probe versus angle of rotation stage is given for the three different E field directions together with the measured noise levels (red curves) . Theoretical fits are also given as dotted curves with pastel solid color backgrounds (± 1.5 dB).

The angular separation between the maxima corresponding to Ex, Ey and Ez corresponds exactly to 120° as expected.

## Specifications of the Ultra Wide Band Triaxial Vector Electric Field Probe

The same triaxial vector electric field probe used for checking its response versus E-field direction @ 250 kHz has been used to carry out a measurement @ 65 GHz. The last figure gives the response of the probe versus the E-field strength @ 160 kHz, leading to a sensitivity of ~ 200 mV/m√ Hz.

## Key features of the Triaxial Vector Electric Field Probe

• vector measurement of the 3 E-field components in ultra small enclosures

• high measurement reproducibility: 0.15 dB

• perfectly adapted for SAR measurement & MRI implant safety assessment in phantoms

• perfectly adapted for E-field vector assessment in atmospheric pressure plasma jet