Electric field measurement at sea

Most of the electrometers are based on the measurement of the difference of potential between two electrodes; a major drawback of this method is its low performance since little of the signal energy is used. Indeed, a very small current goes through the equipment, limited by the high impedance of the voltmeter. The principle described by the author applies to the conducting media where an electric field creates a current density, as shown by the microscopic Ohm´s law; this quantity is measured through an electrode of section S, using all the available energy for the detection: the signal-to-noise ratio is thus rising compared with the preceding approach. In this process, the main difficulty is to guarantee an input impedance equal to the resistance of the water volume substituted by the sensor, i.e. to avoid the current lines disturbance in the medium: this rule is general and applies to any probe of which the presence must not modify the measured value. The main characteristics of the corresponding sensor are presented in this paper; then, the behaviour of a three axis antenna is shown in real conditions-i.e. at sea