Abstract: The invention relates to a device for determining petrophysical parameters of an underground formation, comprising at least two electrodes (EL), a means for emitting a frequency-variable electric current (MEC), and a means for measuring electrical resistivity (MRE) in terms of amplitude and phase, two of the electrodes (EL) cooperating with the emission means (MEC) and at least two of the electrodes (EL) cooperating with the means for measuring resistivity (MRE), a means for measuring a difference in electrical potential (MDP) cooperating with at least two of the electrodes (EL). The invention is particularly applicable to oil exploration and development.

Abstract: Method of exploiting and/or of monitoring the exploitation of a fluid such as a hydrocarbon fluid present in at least one geologic layer of an underground formation. From consecutive pressure and spontaneous potential measurements taken at least at one measurement point in at least one well drilled through at least the geologic layer of interest, the slope of a curve showing the evolution of the spontaneous potential gradient as a function of the pressure gradient is determined. Then, from this slope and from a graph representative of the evolution of the electrokinetic coupling coefficient as a function of the salinity for the layer considered, a salinity value is determined at the measurement point.

Abstract: The invention relates to a system and to a method for measuring at least one flow property of at least one fluid in a porous medium. The measurement system (1) comprises at least one cell (2), means (7) for injecting fluid(s) into the cell and X-ray radiography means (4, 5).

Abstract: Method of exploiting and/or of monitoring the exploitation of a fluid such as a hydrocarbon fluid present in at least one geologic layer of an underground formation. From consecutive pressure and spontaneous potential measurements taken at least at one measurement point in at least one well drilled through at least the geologic layer of interest, the slope of a curve showing the evolution of the spontaneous potential gradient as a function of the pressure gradient is determined. Then, from this slope and from a graph representative of the evolution of the electrokinetic coupling coefficient as a function of the salinity for the layer considered, a salinity value is determined at the measurement point.

Abstract: The invention relates to a device for determining petrophysical parameters of an underground formation, comprising at least two electrodes (EL), a means for emitting a frequency-variable electric current (MEC), and a means for measuring electrical resistivity (MRE) in terms of amplitude and phase, two of the electrodes (EL) cooperating with the emission means (MEC) and at least two of the electrodes (EL) cooperating with the means for measuring resistivity (MRE), a means for measuring a difference in electrical potential (MDP) cooperating with at least two of the electrodes (EL). The invention is particularly applicable to oil exploration and development.

Abstract: The invention relates to a system and to a method for measuring at least one flow property of at least one fluid in a porous medium. The measurement system (1) comprises at least one cell (2), means (7) for injecting fluid(s) into the cell and X-ray radiography means (4, 5).

Abstract: An active implanted medical device, particularly an active implantable medical device, and its external programmer having a bi-directional synchronous transmission of data. The active implanted medical device (10) includes a timing clock (18) and circuits for the emission/reception of signals operating under the temporal control of the timing clock of the active implanted medical device. The programmer (24) includes a timing clock (42) and circuits for the emission/reception of signals, operating under the temporal control of the programmer timing clock.

Abstract: A device for filtering signals emitted by a medical device, principally an active implanted medical device. The device (26) receives an input that is a signal delivered by a circuit (16-24) that receives signals emitted by a medical device (10) in the form of a magnetic induction, in which the medical device has a metallic housing or case. A compensation stage (42) also is provided, having in the frequency domain a transfer function in the form: ##EQU1## where f.sub.c is a chosen parameter according to the geometry and the material of the metallic case of the medical device (10), and where j=.sqroot.-1. The device is useful with medical devices that emit sequences of messages formed by symbols belonging to an alphabet of n symbols (n.gtoreq.2), the compensation stage being able to reduce the rate of inter-symbol interference of collected signals that are applied to it.

Abstract: A device for the reception of signals emitted by an active implanted medical device. The device has a signal collector coil for the reception of a magnetic induction which receives a useful signal component (B.sub.s) emitted by the implanted device (26) and a parasitic signal component (B.sub.p) of external origin. There is at least one collecting coil (12) wound on a first portion (14) of a magnetic circuit and at least one compensation coil (22) wound on a second portion (20) of the magnetic circuit, the two portions of the magnetic circuit belonging to a common magnetic element (16) and being configured in a manner such that, when the device is disposed in face of the implanted device, the collecting coil is essentially crossed one time by the magnetic induction field lines of the useful signal component (B.sub.

Abstract: Process and apparatus for extracting a useful signal emitted by an implanted active medical device in the presence of parasitic signals. This device includes a plurality of signal receivers located at distinct points. The signal receivers are sensitive to the magnetic component of the electromagnetic signals and separated from each other by a distance that is negligible as compared to the wavelength of the electromagnetic signal. A plurality of amplifiers are provided with one amplifier being associated with each signal receiver and each amplifier having an adjustable gain. The amplified signals are summed by an adder, and the summed signal (V(t)) is evaluated using a magnitude (.vertline.V.vertline.) representative of the level of the summed signal.

Abstract: A method and apparatus for measuring an unknown capacitance using a known reference capacitance, wherein a first electrode of the unknown capacitance is connected to ground.

Abstract: A circuit for controlling a ratio meter, the circuit having an input stage for generating a digital signal representative of a parameter to be displayed, memory to enable the digital signal to be encoded on the basis of a pre-defined sine, cosine, or tangent function, with the memory being addressed by intermediate significant bits in the digital signal, and an interpolator for correcting the signal from the memory on the basis of the least significant bits of the digital signal.