Direct Comparison of a Capacitive to an Electro-Optic Electric Field Sensor

A Sensor to measure electric vector fields based on the Pockel effect and a sensor making good use of a search capacitor have been submitted to the same electric field excitations. Outputs of their analog electronics are further processed using a multi-channel dynamic signal analyzer (24 bits and 10 mHz to 100 kHz analysis bandwidth). Both AC and DC behavior have been addressed, the later with the help of an electric field mill. The direct comparison was made possible up to 100 kVm ^-1 using a large enough electric field source and high voltage outputs amplifiers. This way, the sensors are operated at the same time, while occupying similar positions inside the electric field. Results expressed as a voltage transfer function in the AC mode exhibit a good coherence all along the analysis band. It highlights the different bandwidth of the two instruments nonetheless sharing three decades: the search capacitor working at low frequency while the electro-optic one is known to work at high frequency. Finally, the electric field mill used at a chopping frequency of 54 Hz induces a limitation for both sensors in the lower part of their measuring range, below a few hundreds of Vm ^-1 , while noise floors of each sensor are found well below a residual signal induced by the electric field mill rotation.