Abstract: A Pockels effect electric field sensor includes, as a sensitive element, a crystal with electro-optic properties traversed by a luminous beam with specific polarization and propagation directions. The crystal is cut into the shape of an ellipsoid (14) and has a crystallographic symmetry being either uniaxial 622, 422 or 42m or cubic 43m or 23, the three perpendicular axes of the ellipsoid being orientated along three trirectangular crystallographic axes with the highest symmetry of the crystal.

Abstract: A device for measuring electric fields mainly comprises a laser and a probe provided with a centrosymmetric polymer sheet permitting the generation, under the action of the field, of the second harmonic of the emitted wavelength. Optical fibers carry the incident and reflected waves of the laser to the probe and then to an optical measuring cascade. This device is of particular interest for measuring the electric fields between high voltage coaxial cables.

Abstract: A spark ignition system for a gas turbine electronically controls the cycle of charge and discharge of a spark generator of the capacitive type. There is a function generator (5) which derives a reference voltage as a function of the speed of the turbine and possibly of other parameters. A charge control (6) for the capacitive cell (9) and a spark frequency control (7) are controlled by the reference voltage. Reignition in the case of flame extinction is controlled by an opto-electronic arrangement (11, 12, 13) which drives a reignition circuit (14), when flame extinction is detected. The reignition circuit produces a voltage which is superimposed on and over-rides the speed reference voltage to activate the system to produce ignition at a start condition.The system can be used for ignition of a gas turbine, especially a turbo-compressor.