Abstract:
A device for coupling several data processing units to a central memory, the processing units being each provided with means for exchanging data with peripheral devices and with computing means, the device includes management means for controlling the sequential execution of orders issued from the memory, according to a hierarchical classification of the lists of tasks for the exchange processes and the computing process and further includes devices for commutation upon control of decoding means of a signal produced by the processing units, in accordance with the value of a binary digit associated to a task of a fresh list of actuatable tasks established in a non-hierarchical system.
Abstract:
The invention relates to the measurement of the difference between refractive indexes of two media, traversed by a light beam the beams produce an interference figure consisting of fringes having a displacement which is measured.According to the invention, the displacement of the fringes of the interference figure is detected with a photosensitive device and a phase modulation is performed on at least one of the beams and the modulation is controlled in order to obtain a movement of the fringes of the interference figure.
Abstract:
A process for optimizing the transmission rates of digitized signals on transmission lines in multifunction cables, such as logging cables linking well tools to surface installations. The process includes digitising of the data to be transmitted and coding thereof through voltages selected from a set of multilevel coding voltages (2 to 32 for example), and widening towards high frequencies of the passband of each transmission line used, by combination with correcting circuits selected so that the transfer function of the corrected line is substantially that of a filter of the Bessel type, at least in a given frequency range on either side of a 3-dB cut-off frequency fc which depends on the number of coding voltages and on the amplification parameters. Using this process makes it possible to exceed very easily a total flow rate higher than one Mbits/s without increasing the transmission error rate.
Abstract:
Method and device for the high-rate transmission of data between a multiplicity of acquisition apparatuses (Ai) and a central station to which they are connected by a common transmission channel (V1) for commands and by a high-rate transmission channel (V2) for data.A first clock signal (H1) serves for the transmission of the orders, the acquisition of the data and their storage in a memory (10). A second clock signal (H2) with a higher frequency non synchronous with the first one is used for reading the data stored by each acquisition apparatus. A determined time interval (or window) is assigned to each apparatus and the reading of each stored sample is activated by an order signal indicating the beginning of this window.Application to a seismic transmission system for example.
Abstract:
A signal sensor automatically compensates for the variations of the static pressure of the medium in which it is placed. The signal sensor comprises one or two assemblies each formed of a piezoelectric sensitive element applied against one face of a flexible plate. The other face of the plate is shielded from the variations of the dynamic pressure to be measured by a material absorbing the vibrations but fairly flexible so as to transmit any variation of the ambient static pressure. This material which may be a porous foam or a fibrous substance impregnated with liquid, fills a tubular apertured sleeve.
Abstract:
An acquisition device for digitizing highly dynamic signals. After amplification in a fixed gain amplifier, the signals are applied to a sample and hold unit, the output of which is connected to an analog-to-digital converter to which a variable reference voltage is applied. This reference voltage is available at the output of a multiplexer to the inputs of which voltages are applied derived from sub-divisions of a calibrated voltage. The choice of the reference voltage is effected by a logic assembly as a function of the comparisons made by comparators between the sampled voltage and the derived voltages. The digitized signals are represented by a digital word from the converter and a digital word of gain G from the logic assembly.
Abstract:
An improved device for sampling signals to minimize the errors introduced in the stored samples includes first and second sampling elements whose respective sampling and holding periods are offset with respect to each other, an amplifier applying a gain G to the difference between the input voltage and the sample stored by the first element, before transmitting it to the second element, and a summing circuit for adding to the samples stored by the first element a fraction of the samples stored by the other element. The sampling errors are reduced by a factor G equal to the gain value.
Abstract:
Piezoelectric transducer for the production of, for example, hydrophones, with the transducer including a plurality of sensitive coaxial elements interconnected so as to compensate for the effects of accelerations and deflections.A transducer includes at least one pair of sensitive elements composed of sections of radially polarized coaxial piezoelectric cables having an opposing orientation, with an external armouring of one being connected with an internal armouring of the other, and vice versa. By increasing the number of parts of sensitive elements and selecting the relative disposition, it is possible to improve the immunity of the transducer to noise due to accelerations and deflections, regardless of the direction or the need to license a direction where the transducer is sensitive to such noise. A predetermined number of pairs of sensitive elements can be combined around a central column for accommodating connectors or cables.To be applied, for example, to the production of hydrophones.
Abstract:
A two stage, decentralized device for transmitting seismic data information from seismic receivers of a seismic streamer to a central recorder on a ship, including a series of interconnected sections each having a plurality of seismic receivers distributed over it's length, seismic signal acquisition apparatus for digitizing and storing seismic signals coming from a group of seismic receivers to which a respective seismic signal acquisition apparatus is connected, central control and recording device on the ship and assembly of electronic modules each disposed in the vicinity of a seismic receiver and being capable of amplifying and filtering the seismic receiver signals.
Abstract:
A device is provided for interconnecting a series of data acquisition apparatuses. Each of the apparatuses collect signals and transmit them to a remote central receiving and recording system. In order to sequentially transmit the signals thereto on reception of an order from said central system, the apparatuses are subdivided into a plurality of groups having the same number m of apparatuses. The groups comprise cable sections of substantially equal length interconnecting the acquisition apparatuses in such a manner that the apparatuses of the same rank of each group are connected in parallel by the same transmission cable to the central system.