Abstract: A test procedure or test station for testing products, especially products completed on an assembly line type production process, performing the following steps: First, testing a parameter of a product with a first testing device using a first input signal to produce a first test result. Second, testing the same parameter of the product with a second testing device using a second input signal that is independent of the first input signal to produce a second test result. Third, deriving a differential value from the test results obtained by the testing devices. Fourth, determining the conformance of the testing station from the differential value and outputting an error message when the differential value deviates from a predetermined range. Fifth, repeating above steps for at least one other parameter.

Abstract: A circuit for the conversion of an electrical input signal into an optical output signal is disclosed. A portion of the main beam from a laser diode that provides the optical output is reflected to a PIN diode with a glass pane. Linearization of the electro-optical conversion process over a wide frequency range is achieved through a feedback loop. For operation at frequencies higher than that of the feedback loop bandwidth, the various conversion factors for low and high frequencies can be additionally adapted.

Abstract: A high-pressure viscous damper is proposed, in particular for use in liquid chromatographs, in which two chambers are separated by an elastic partition, and the one chamber receives a fluid to be damped and the other chamber holds a damping fluid. In the chamber holding the damping fluid an insert is provided within the fluid with a selected volume and temperature expansion coefficient so that by the combination of the insert and damping fluid and the volume and wall material of the second chamber a volume compensation is achieved.

Abstract: In a four element modified bridge circuit for measurement purposes at least one impedance element is variable according to a magnitude to be measured. Via a first operational amplifier a DC supply voltage is connected across two bridge nodes facing each other, and at the other two nodes facing each other an output signal is delivered corresponding to the magnitude to be measured. By means of a second operational amplifier one of the output nodes is virtually drawn to ground so that the signal at the second output bridge node is referenced to ground. Thus, the signal at the second output node corresponds to the desired measured magnitude without a superimposed power supply voltage and may be amplified by a third standard operational amplifier without the need of a differential amplifier circuit.

Abstract: A linear regulated D.C. power supply includes two control elements for regulating two separate unregulated D.C. voltage sources. An enabling means is used to enable the one of the two control elements which is operating at the lower instantaneous power dissipation level and to supply the regulated output of that selected control element to a load.

Abstract: A respiration monitor for detecting effective respiration of a patient includes circuitry for suppressing the indication of unwanted signals due to heart activity, noise and flat breathing. A first threshold circuit is provided for increasing the sensitivity of the respiration monitor in response to a decreasing amplitude of the measured respiration signals. A first comparator circuit provides a fixed amplitude threshold below which detected signals are fully neglected. A second threshold circuit provides an adjustable amplitude threshold for the measured respiration signal, which threshold is raised in response to a decreasing respiration frequency below a predetermined frequency limit. Effective respiration is indicated only if all the aforementioned amplitude thresholds are exceeded.

Abstract: A pulse generator circuit generates pulses or logic signals with variable upper and lower levels. According to a preferred embodiment of this invention there are provided two variable voltage sources representing variable logic state levels. For alternately connecting these voltage sources with the output of the circuit there is provided a diode bridge in the configuration of a Graetz rectifier with two nodes connected to these voltages sources and the other two nodes forming complementary output signals; these latter two nodes are also connected to equal and opposite constant current sources which are reversible in accordance with a control signal. The voltage sources are coupled to the bridge via operational amplifiers configured as voltage followers. In each associated feedback loop of the voltage sources there is a diode substantially identical to those of the bridge which is coupled to a constant current source equal in magnitude to those of the constant current sources connected to the bridge.

Abstract: A thermostat arrangement for the mobile phase and the separation column in a liquid chromatograph comprises a heat exchanger through which the mobile phase passes. The heat exchanger has a heating and/or cooling element and is arranged between a sample injection device and the entrance of the separation column. The heat exchanger serves to selectively heat or cool the ambient air surrounding the separation column.

Abstract: A read/write circuit for a random access memory comprises mode switching means for placing the memory into a read mode if an external read request signal is received and for placing the memory into a write mode if an external write request signal is received. A priority circuit controls said mode switching means and prevents it from placing the memory into the read mode as long as a write request signal is present and enables said mode switching means for placing the memory into the read mode after each write operation has been completed. A read-out control circuit is responsive to the read request signal for enabling a read operation at the next following read mode enabling and for repeating the read operation at the subsequent read mode enabling if the read operation was not completed before the termination of the read mode enabling.

Abstract: A circuit for converting a triangular waveform into a sinusoidal waveform using the non-linear transfer characteristic of a first transistor differential amplifier. Second and third differential amplifiers are parallel-connected to said first differential amplifier with the slopes of their transfer characteristics in opposite sense thereto and having their operating points shifted on their transfer characteristics in opposite directions with regard to each other and symmetrically to the operation point of said first differential amplifier so that the resulting overall transfer characteristic of said first, second and third differential amplifiers has zero slope at the extremal amplitudes of said triangular waveform.

Abstract: An apparatus for solvent degassing and solvent supply in a liquid chromatograph comprises at least one solvent storage vessel, the volume of which is partly filled with liquid solvent while the remaining volume forms a vapor volume. A helium source is connected to said vapor volume for avoiding re-absorption of air by the solvent. A vacuum pump is connected to said vapor volume via a suction line, and a solvent source is connected to said vapor volume via a supply line. A pore filter terminates said supply line within said vapor volume.

Abstract: A pulse generator circuit comprises a pulse source and an output line having a specific characteristic impedance and having an input and an output end, the output end being connectable to a high impedance external load and the input end being connectable to and disconnectable from said pulse source. An internal impedance being substantially equal to said characteristic impedance is provided and is connectable to and disconnectable from said input end of the output line. The input end of the output line can be alternatively connected to either the pulse source or to the internal impedance by a switching means. The switching means is controlled by control means in such a way that during delivery of pulses by said pulse source the pulse source is connected to said input end of the output line whereas said internal impedance is connected to the input end substantially during the intervals between the pulses.

Abstract: A pulse generator for generating pulses having predetermined slopes is disclosed, comprising a capacitor that can be charged and discharged through predetermined current sources, a switching device for connecting and disconnecting the current sources and a step function signal source for controlling the switching device. The capacitance of the capacitor is in the range of the stray capacitance of the switching device. A fraction of the output signal of the step function signal source is superimposed in oppposite phase upon the output signal of the capacitor so as to compensate the voltage surge in the output signal of the capacitor resulting from the voltage divider formed by the stray capacitance of the switching device and the capacitor.

Abstract: A method for linearizing the exponential characteristic curve of an electronic component, in particular the temperature/resistance characteristic of a thermistor is provided. The output value of the component is compared with the output value of a reference circuit varying exponentially in time and in the same sense as said characteristic, and the time interval is measured between a fixed starting moment, at which the exponential variation is already taking place, and the moment when the two output values become equal.

Abstract: A dosing device for a liquid chromatograph includes an axially movable shank. The shank is guided in packing sleeves and has a notch or cavity for receiving a sample and transferring it between a sample chamber and a high pressure chamber by axially moving the shank. The high pressure chamber is coupled to the chromatograph flow system between the pump and the column. A shutter is provided for closing the notch. In the closed position, the shutter and the shank together form a smooth common surface.

Abstract: A respiration monitor for measuring the variations of the thorax impedance of a patient due to respiration activity includes circuitry for suppressing the indication of unwanted signals caused by the activity of the heart. This circuitry is connected to receive separate signals corresponding to the heart beat rate and compare the periods of these signals to those of the signals measured at the thorax of the monitored person. If the periods of both signals are substantially equal, i.e. the signals measured at the thorax are actually due to heart activity rather than to respiration, the trigger threshold value of the monitor is automatically and stepwise raised so that the monitor does no longer respond to heart beat related signals but indicates that no respiration signals are measured.