A sensor for sensing an electric field includes a movable sensor probe including one or more pair, typically three pair, of electrically conductive electrodes, and may include one or more pair of selectively switchable auxiliary electrodes. The probe is movable and may be mounted on a vehicle or trailer. A processor may process electric field signals from the probe for providing a human perceivable indication of the electric field. The processor may perform a Fast Fourier Transform of the electric field signals to produce an indication of the magnitude of the electric field, and may perform unweighted and/or weighted averaging in relation to processing electric field data, setting a comparison threshold, providing a human perceivable indication, or a combination of the foregoing. A speed at which the sensor probe is moving may be utilized in processing the data.