Abstract: A signal processing circuit, including at least two stages of frequency modulation (25,20; 28, 31, 33) and demodulation of signals applied to or generated within that circuit, characterized in that the modulating and demodulating signal for each stage is an effective square wave and in that the ratio of the frequencies (F1, F2) of the modulating signals for the first and second stages corresponds substantially to the ratio of an even integer to an odd integer, or vice versa, such that there are substantially no common frequencies or harmonics between the first and second modulating signals.

Abstract: A device for measurement of electrical energy having current and voltage sensors 1, 2, a multiplexing circuit 8 and an analogue to digital converter 11. A microprocessor 9 controls the multiplexing circuit in order to supply the current and voltage signals alternately to the converter 11, the microprocessor 9 calculating the electrical energy at a moment in time using two values of the voltage situated around a current sample and using three samples of the current. By these means the time delay between samples of the voltage and current can be corrected.

Abstract: An electricity meter and method for measuring VA power consumption. The electricity meter comprises a transducer circuit receiving line current and line voltage and producing a first signal corresponding to active power on the line, and a level shifting circuit responsive to the first signal for producing a second signal corresponding to apparent power.

Abstract: The invention relates to a tool suitable for closing a production column (100) of a well when the tool is located in a connector of enlarged diameter (101). The tool is lowered on the end of a cable (76) and includes a tilting valve member (60) which is oblong in shape and which is oriented longitudinally to pass through the corresponding oblong orifice of a valve seat (69) fixed to the connector, and is then oriented transversely in order to co-operate with said seat in order to close the production column when a traction force (F) is applied to the cable (76).