Mettler Instrumente Ag

Cerberus Ag

Mettler Instruments Ag

Mettler-toledo Ag

Siemens Building Technologies Ag

Mettler-toldedo Ag

Peter Kunz

Dieter Wieser

Felix Strobel

Kurt M&uuml;ller

Tadeusz Wojnarski

Markus Loepfe

A detector device for detecting the presence of airborne particles such as smoke includes a light source, an optical bridge, a measurement path, a reference path, a measurement receiver and a reference receiver. The optical bridge, in addition to the light source and the measurement and reference receivers, are the only optical elements of the detector device. The optical bridge includes two circular apertures arranged downstream of the light source along the radiation path. The light source is arranged in a chamber having an air reservoir, whose surface area is substantially greater than that of the light source. A temperature drift curve is determined by heating the light source and storing the detector signal at different temperatures.

Optical smoke detector operating in accordance with the extinction principle and method for compensating its temperature drift

The smoke detector includes a light source (1), a measurement section (3) with a measuring receiver (5), a reference section (2) with a reference receiver (4), and an analyzer circuit (6) connected to the receivers. The receivers are of like construction and receive like amounts of radiation from the light source (1). A difference signal (.DELTA.I) formed from the current signal (I.sub.r) of the reference receiver and the current signal (I.sub.m) of the measuring receiver is fed to the analyzer circuit. A reference current (I.sub.k) is superimposed upon the current signal (I.sub.r) of the reference receiver, and the light source is connected to a control circuit and regulated by the control circuit for compensation of the reference current (I.sub.k) by the reference current signal (I.sub.r). The difference signal (.DELTA.I) is superimposed with a compensation signal (I.sub.k ') for zero compensation.

Optical smoke detector operating in accordance with the extinction

Active IR intrusion detector

Weighing apparatus of the electromagnetic load compensation type includes a ferromagnetic yoke member (19), that is secured at a single point to the frame (3), thereby a permit the frame to be formed of a non-ferromagnetic material, such as aluminum, having a different coefficient of expansion than the yoke member. Preferably the yoke member is secured to the frame by a single screw (33,103) arranged at the axis of symmetry of the yoke member. Owing to the small contact surface between the yoke member and the frame, the production of temperature-responsive forces which would otherwise stress or distort the apparatus to adversely affect the accuracy of the weighing operation is avoided.

Weighting scale having improved yoke mounting means

A draft protection device for a precision balance includes a base and a stationary rear wall connected to the base. The top of a front pane is connected through two connecting bars to the rear wall. The draft protection device further includes two sliding doors which are slidably mounted in longitudinal guides in the connecting bars and in the base. Racks are mounted in the areas of the upper edge and of the lower edge of at least one of the sliding doors. Pinions connected to each other through a vertically extending shaft mounted at the rear wall mesh with the racks. The shaft may be driven by an electric drive.

Draft protection device for a precision balance

A weighing apparatus comprising a first self-contained weighing device (1) including a first farme (2), a first load-receiving member (5) connected by a parallel guide arrangement for movement from a normal no-load position relative to the first frame, a load-responsive device (10) for indicating the magnitude of an applied load as a function of the movement of the first load receiving member, and a first motion-transmitting lever (7) connected between the first load receiving member and the position-responsive device, characterized by the provision of a second load receiving member (16,28) to which the load to be measured is applied, and a second pivotally mounted motion-transmitting lever (17,30) connecting the second load receiving member, thereby to provide a resultant load range that is higher than that of the first weighing device. Thus, various increased load ranges may be achieved starting from a standard self-contained weighing apparatus. Moreover, a calibration weight (23) may be applied to the first load receiving member at a position other than that at which the load to be weighed is applied.

Weighing apparatus having multi-range motion transmitting levers

Weighing apparatus of the load compensation type includes a source of constant current pulses the duration of which is determined by a regulating signal in response to the position of the load receiver relative to the frame, thereby to maintain the load receiver in an initial or zero position during the application thereto of a load to be measured. The regulating circuit includes a PID regulating amplifier that produces a differential signal (D) and a proportional and integral signal (PI). The PI signal controls the operation of a switch that determines the duration of the constant current pulses, and the D signal modulates the amplitude of the constant current from which the pulses are formed. In this manner of using the differential regulating signal component (D), the influence of various deleterious effects on the weighing apparatus, such as vibration, is avoided.

Weighing apparatus with improved electromagnetic load compensation

Electronic weighing apparatus includes an adjusting arrangement for vertically adjusting relative to the scale frame at least one of the resilient bending bearings that supports one end of a guide member of the parallelogram arrangement that guides the load receiver for vertical movement relative to the frame. Preferably, the adjusting device includes a cantilevered resilient auxiliary guide plate arranged in parallel relation between the upper guide member and the frame; the upper guide member being arranged in a recess contained in the adjacent surface of the guide plate. At its end, adjacent the load receiver, the cantilevered guide plate is connected with the frame. At its opposite end, the guide plate extends in spaced relation to the frame, an adjusting screw being provided for vertically adjusting the opposite end portion relative to the frame as well as the bending bearing associated therewith. Cover members are provided for covering the recess and the guide members to facilitate uniform temperature distribution in both guide members.

Electronic weighing apparatus including guide adjusting means

An electronic balance includes a measuring cell for electromagnetic load compensation. The measuring cell and a load receiving member of the balance are arranged in an inner housing which is closed to all sides with the exception of an opening for a receiving cone of the load receiving member. The inner housing is mounted in the balance housing so as to be spaced apart from the walls, the base and the cover of the balance housing. A circumferentially extending partition wall is tightly sealingly attached to the bottom and the cover of the balance housing. The partition wall is mounted between the inner housing and the walls of the balance housing.

Electronic balance

A scale of the platform type includes a base frame, a lever mechanism for force-transmission connected to the base frame, and including a plurality of two-armed levers, a weighing platform supported by the two-armed levers, a measurement transducer disposed within the base frame and adapted for generating signals substantially proportional to a weight placed on the weighing platform, and a movable load-carrying frame surrounding the base frame, and wherein each two-armed lever is pivoted on the base frame. This concept permits attainment of scales of very low height, hardly sensitive to corner loads, namely loads offset from the center of the scale, and which have a high degree of resolution. The scale may be used for precision weighing, and may have a load region e.g. within a range from about 10 kg to about 100 kg.

Platform-type scale

Weighing apparatus of the load compensation type including a position sensing circuit for supplying current pulses from a constant current source to a compensation coil to return the load platform--after the application of a load thereto--toward its initial no-load position relative to the frame, the magnitude of the compensation current, as displayed by digital readout means, being a function of the mass of the applied load, characterized by the provision of an auxiliary analog-to-digital converter for digitalizing a signal corresponding with the compensation current, and a comparison circuit for comparing the digitalized signal with a standard value and for generating an error signal if the comparison result exceeds a given value. In addition to monitoring the constant current source, other components (such as temperature sensor, current switch and compensation coil) may be monitored by corresponding comparisons.

Weighing apparatus and method for automatically monitoring a constant

Weighing apparatus of the electromagnetic load compensation return-to-zero type including a vertically displaceable load support member to which is connected a load compensation coil arranged for movement in a stationary magnetic field, characterized in that the magnetic field is produced by at least one permanent magnet mounted in a hollow yoke structure defined by a pair of U-shaped yoke members each formed of a ferromagnetic material. The yoke members are arranged in opposed coaxial relation with their leg portions being parallel and extending toward each other. The yoke members are relatively angularly displaced about their common axis through an angle of 90.degree., the leg portions of one yoke member extending between the leg portions of the other member. This design affords improved ease of assembly of the weighing apparatus and avoids the use of an additional magnet screen, thereby reducing the height of the yoke since the substantially enclosed hollow yoke structure has only a very small stray magnetic field.

Weighing apparatus including improved yoke construction

In a scale wherein the force or load receiver is guided along a vertical path by a parallel guidance system having an upper and a lower plate, the lower plate cooperates with a recess in the lower part of the housing to form an air damper. Specifically, the lower plate of the parallel guidance system constitutes the piston of the air damper. For the scale with a capacitive sensor, the plate constituting the piston of the air damper is a metallic plate which also constitutes the movable plate of the measuring capacitor.

Scale with simplified guidance-damper construction

A weighing apparatus of the electromagnetic load compensation type is disclosed, including a housing, a load receiver connected for vertical movement relative to the housing, a permanent magnet system connected with the housing for establishing a permanent magnetic field, and an electromagnetic compensating system including a compensation coil connected with the load receiver for movement within the magnetic field. The invention is characterized in that--in order to simplify manufacture and assembly while also achieving low structural height-the permanent magnet system includes a hollow sectional open-ended soft iron yoke member having a generally rectangular cross-sectional configuration, which yoke member is formed from a pair of longitudinally extending generally identical sections. At least one flat permanent magnet is mounted on the inner surface of the yoke member for establishing a flux path therein to generate the magnetic field.

Weighing apparatus including a sectional yoke member

An improved weighing apparatus of the electromagnetic load compensation type is disclosed, characterized by the provision of a stationary permanent magnet system including two oppositely arranged pairs of spaced parallel flat magnet members that cooperate to define a common air gap. The compensation current coil, which is connected for movement with the movable load-receiving member, is of a flat annular configuration and is contained in the plane of the air gap extending between the magnet members of each pair. The magnet members of one pair are magnetized oppositely from those of the other pair, whereby the magnetic field established across the portion of the air gap between the permanent magnet members of one pair is of a direction opposite that established between the permanent magnet members of the other pair. Consequently, not only can the compensation current for a desired compensation force effect be reduced, but also, the manufacture of the permanent magnet system is greatly simplified.

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Gossau, Switzerland

Peter Kunz