The RadiSense probe is always measuring in rectangular coordinates, since all three axis’ are orthogonally aligned. In theory it does not matter how the sensor is placed in the field, it should always indicate the same total E-field.

The total field is calculated by Etot = SQRT (Ex² + Ey² + Ez²).

Nevertheless, no E-field sensor is perfect due to probe shape, probe dimensions, field perturbation and anisotropy small errors will exist. Therefore, it is recommended to place one of the axis’ parallel to the field. This can be accomplished by placing the sensor in such a way that one element has the same direction as the elements of your radiating antenna.