Abstract: Radiometer for the determination of a temperature of a body by measuring emitted thermal noise and measurement process using this radiometer. The radiometer includes a double radiofrequency signal amplification chain (1) for thermal noises, one of whose branches (2') continuously measures a thermal noise signal generated by a predetermined reference source (3), two converter circuits (5, 5', 6, 6') whose continuous signals are transmitted to a unit (8) for control, processing and evaluation, and means (9, 10, 11) for changing the heterodyne frequency transposition of the radiofrequency signal frequencies of the thermal noise processed in the two branches (2 and 2').

Abstract: A process for frequency tuning microwave bridges and a device for practicing such a process. The process is characterized in that it consists in subjecting a resonator (3) to the radiation delivered by a secondary microwave source (10) sweeping a wide band of frequencies comprising particularly the frequency (F) of radiation delivered by the principal microwave source (1). The radiation reflected by the resonator (3) is displayed and the relative positions are marked along the frequency spectrum, of the frequency (F) and of the frequency of resonance (Fr) of the resonator (3). The frequency (F) of radiation delivered by the principal microwave source (1) is varied while controlling in real time the effect of this variation on the relative positions of the frequencies (F and Fr).

Abstract: Device and process for the generation of amplitude-modulated radiofrequency excitation pulses. A first unit (2) delivers a radiofrequency signal of constant level and a second unit (3) delivers a modulation signal of the radiofrequency signal, formed from numerical data. At least two analog multipliers (6) are connected in cascade as to the radiofrequency signal (RF) from the first unit (2) and are supplied in parallel by the modulation signal (SM) from the second unit (3). For n multipliers (6) in cascade, with n.gtoreq.2, the modulation signal (SM) delivered to the n multipliers (6) is of the A.sup.1/n.f(t) type, A.f(t) being the desired resulting modulation signal (SMR). The second unit (3) is a memory (4) containing point by point the envelope of the modulation signal A.sup.1/n.f(t) and a digital/analog converter (5) whose output is connected to the inputs in parallel of the n analog multipliers (6) in cascade.

Abstract: Process for the excitation and acquisition of NMR signals, particularly for the analysis of molecules dispersed in a solvent, such as for example water. A specimen to be analyzed is first subjected to a series of impulses (1) corresponding to a high resolution NMR test to be carried out. Then there is applied to the specimen a first pulsed field gradient (2) in a given direction, and then the specimen is subjected to a 180.degree. selective pulsed radiofrequency field (3) affecting all the spectrum except the resonance frequency of the water or corresponding solvent. Then a second pulsed field gradient (4) identical to the first is applied to the specimen. Then the acquisition and processing of the resulting NMR signals are effected.

Abstract: Commutation device to connect and disconnect a current or voltage generator and a coil adapted to create a gradient of magnetic field in a measurement chamber of an NMR apparatus. The device comprises a switch (1) mounted in the supply circuit (2) of the coil (3), actuated by a control signal and adapted, in open position, to isolate totally the coil (3) from the generator (4). The switch is a double switch (1) adapted to separate, upon opening, the supply circuit (2) into a portion (5) connected to the generator (4) and a portion (6) connected to the coil (3), independently of each other. Alternatively the switch can be a high speed switch comprising at least one field effect transistor.

Abstract: A cold junction compensation device for a thermocouple, comprising a thermostatically interface casing (1) receiving directly the wires (3, 3') of the thermocouple (2) and ensuring the interconnection of these latter with an extension cord (4). The interface casing (1) contains moreover a cold junction compensation circuit (5).

Abstract: A hyperfrequency generator comprising a source element (5) of negative resistance adjacent to a cylindrical resonant cavity (2) closed at opposite ends by two transversal closure plates (4, 7) for the purpose of tuning over a frequency band. The source element (5) is installed directly in the resonant cavity (2) such that there is a direct coupling between the source element (5) and the resonant cavity (2). One of the closure plates (7) is movable toward and away from the other for rough tuning.