Abstract: A method for measuring a flow of a fluid in a tube includes heating the fluid in the tube with a heating element. A first signal is measured with a first temperature sensing element at a first location. A second signal is measured with a second temperature sensing element at a second location. At least one temperature signal is calculated based on the first signal and the second signal. The at least one temperature signal includes a difference temperature signal and a sum temperature signal. The difference temperature signal is calculated based on a difference between the second signal and the first signal. The sum temperature signal is calculated based on a sum of the second signal and the first signal. The flow is derived based on the difference temperature signal, the sum temperature signal, or a combination thereof.

Abstract: A method for measuring a flow of a fluid in a tube includes heating the fluid in the tube with a heating element. A first signal is measured with a first temperature sensing element at a first location. A second signal is measured with a second temperature sensing element at a second location. At least one temperature signal is calculated based on the first signal and the second signal. The at least one temperature signal includes a difference temperature signal and a sum temperature signal. The difference temperature signal is calculated based on a difference between the second signal and the first signal. The sum temperature signal is calculated based on a sum of the second signal and the first signal. The flow is derived based on the difference temperature signal, the sum temperature signal, or a combination thereof.

Abstract: A control arrangement for controlling a piston pump unit for liquid chromatography, in particular high-performance liquid chromatography, is described. The piston pump unit has at least two piston-cylinder units which operate cyclically in a phase-offset manner and generate, at an outlet port, a predetermined flow of a liquid medium to be delivered. A system pressure is established at the outlet port, irrespective of an associated fluid load resistance. The control arrangement is configured to record the pressure in the cylinder volume of at least a first of the at least two piston-cylinder units. During a measurement phase of the compression phase of the first piston-cylinder unit or during a measurement phase of the decompression phase of the first piston-cylinder unit, the control arrangement stops the drive device for the first piston-cylinder unit for a predetermined time period and in the process records measurement data which characterize the time profile of the pressure.

Abstract: A control arrangement for controlling a piston pump unit for liquid chromatography, in particular high-performance liquid chromatography, is described. The piston pump unit has at least two piston-cylinder units which operate cyclically in a phase-offset manner and generate, at an outlet port, a predetermined flow of a liquid medium to be delivered. A system pressure is established at the outlet port, irrespective of an associated fluid load resistance. The control arrangement is configured to record the pressure in the cylinder volume of at least a first of the at least two piston-cylinder units. During a measurement phase of the compression phase of the first piston-cylinder unit or during a measurement phase of the decompression phase of the first piston-cylinder unit, the control arrangement stops the drive device for the first piston-cylinder unit for a predetermined time period and in the process records measurement data which characterize the time profile of the pressure.

Abstract: An autosampler for high-performance liquid chromatography (HPLC) with a high-pressure injection valve (1, 2) having improved life, particularly in high pressure operation. The geometry of the valve components and the connections of the high-pressure injection valve are provided such that the switching processes do not take place in a deleterious direction. The grooves in rotor (2) and/or the port opening cross sections (131, 151) in stator (1) and the rotational direction are selected such that fluid flows from grooves under high pressure in the direction of narrow, substantially pressure-free ports are avoided. This applies in particular to the switching process from INJECT to LOAD, since the sample loop contains a relatively large dead volume of compressed fluid. In addition, the valve can be controlled according to the invention in such a manner that an appropriate time is available for reducing harmful or undesired pressure differences.

Abstract: The invention relates to an autosampler for high-performance liquid chromatography (HPLC) with a high-pressure injection valve (1, 2) that has a considerably improved service life in comparison to the prior art, particularly in operation at very high pressures. This objective is achieved according to the invention by adapting the geometry of the valve components in such a manner and establishing the connections of the high-pressure injection valve in such a manner that the switching processes do not take place in a direction that reduces the service life. The grooves (81, 83, 85; 61, 63, 65; 21, 23, 25) in rotor (2) and/or the port opening cross sections (131, 151) in stator (1) and the rotational direction are selected such that fluid flows from grooves (81, 83, 85; 61, 63, 65; 21, 23, 25) under high pressure in the direction of narrow, substantially pressure-free ports (11, 12, 13, 16) are avoided.

Abstract: The invention relates to a method for providing a defined fluid flow, especially for use in liquid chromatography. According to the method, a constant total flow (f0) is subdivided into an internal excess flow (fie) in an excess branch and into an internal working flow (fiw) in a working branch. The ratio of subdivision of the internal working flow (fiw) and the internal excess flow (fie) depends on the reverse ratio of a fluidic resistance provided in the working branch and a fluidic resistance in the excess branch. The excess branch and the working branch are interlinked at the respective outputs of the two fluidic outputs of the fluidic resistances by a cross-branch. The equalizing flow occurring between the outputs of the fluidic resistances is measured by means of a flow sensor. A desired, external working flow in the further course of the working branch can be fed to a working device, for example a chromatography column mounted downstream of the device.

Abstract: The invention relates to a method for providing a defined fluid flow, especially for use in liquid chromatography. According to the method, a constant total flow (f0) is subdivided into an internal excess flow (fie) in an excess branch and into an internal working flow (fiw) in a working branch. The ratio of subdivision of the internal working flow (fiw) and the internal excess flow (fie) depends on the reverse ratio of a fluidic resistance provided in the working branch and a fluidic resistance in the excess branch. The excess branch and the working branch are interlinked at the respective outputs of the two fluidic outputs of the fluidic resistances by a cross-branch. The equalizing flow occurring between the outputs of the fluidic resistances is measured by means of a flow sensor. A desired, external working flow in the further course of the working branch can be fed to a working device, for example a chromatography column mounted downstream of the device.

Abstract: The invention concerns a process and a device for the splicing of optical fibers. At least one laser beam is directed to the optical fibers for the thermal splicing of at least two optical fibers. According to the invention, the position of an impingement point of each and every laser beam onto the optical fibers is periodically changed in the longitudinal direction of the optical fibers to be spliced for the impact of the power density profile onto the optical fibers to be spliced.

Abstract: An optical coupling device for coupling light in between two optical waveguide end faces, in which the geometric position of one optical waveguide end face can be varied with respect to the other optical waveguide end face with the aid of a variable-length element. The element carries one of the two optical waveguides, and is connected to the other optical waveguide via a holding block. The variable-length element is connected to a variable-length compensating element, whose length changes with temperature by the same amount but in the opposite sense as that of the variable-length element. The variable-length compensating element is fixed to the second holding block.

Abstract: A test optical fiber section (F) that resides under tensile stress (F) is heated in at least one longitudinal location so that a constriction (&Dgr;d) of its outside circumference forms thereat. This constriction (&Dgr;d) is acquired and utilized for setting welding parameters.

Abstract: Two contacting test fibers that are radially offset relative to one another with a prescribable initial offset are heated such that an offset-reducing effect occurs. The resultant reduction of the initial offset is utilized for setting, particularly optimizing welding parameters.

Abstract: Two incipiently fused fiber ends are fused to one another by being pushed one inside the other in a longitudinal direction beyond the end face contact site by a variable amount, which is increased in proportion to the greater extent of the poorer quality of the end face as compared to the desired shape of the end face.

Abstract: To compensate for disturbing influences during arc welding of at least two optical waveguide fiber ends, an impedance of the discharge path of the arc is measured and at least one of the welding parameters is varied based on the measured impedance.

Abstract: A method for recognizing an angular error between a fiber end, which is aligned with another fiber along a desired axial orientation, by scanning one of the optical fibers along a scanning path, shifting the fiber to a second position in a direction parallel to the desired axial orientation for the fiber and scanning the optical fiber in the second position along the same measuring path, evaluating the intensity of each of the scans to determine the skewed angle for the fiber from the desired axial orientation.

Abstract: A method and apparatus for measuring a plurality of light waveguides includes a coupling device having an arrangement for conducting a light spot in a chronological succession along an infeed section of the plurality of waveguides for coupling light therein and an outcoupling region, wherein the reception radiation fields are acquired in terms of their chronological distribution and their chronological distribution is evaluated.

Abstract: An apparatus for performing measurements on a plurality of light waveguides comprises an arrangement for coupling distinguishably fed optical signals into each of the waveguides and measuring each of the distinguishable signals from the waveguides by using flexural couplers. In one embodiment, the distinguishable signals are obtained by utilizing modulated signals of different modulations, or different frequencies. In another embodiment, the signals are sequentially applied in a chronological order to the waveguides and are separately evaluated.

Abstract: A method and apparatus for measuring the attenuation of optical medium utilizing a transmitter and a receiver arranged on each side of the medium. In the method, two-measurement series are acquired in succession and the reception signals thereof are derived both from the series using reception signals from both the right and left-hand transmitters on a first receiver, while the second receiver is uncoupled. Then, a second series is performed with the second receiver coupled in and the first receiver uncoupled.

Abstract: During an initial pressure application on a light waveguide with a coating, which waveguide is subjected to a flexional coupling, deformation of the coating will occur and the value of an outfed light from the light waveguide will change as the deformation changes. The final intensity of the outfed light is obtained during the deformation of the coating by a process of extrapolating the final value from the initial measured values occurring during the initial deformation of the coating.