Mettler-toledo Gmbh

Mettler-toledo Ag

Christoph Trautweiler

Hans-Rudolf Burkhard

Daniel Schrag

Daniel Rupp

Douglas Bliss

Cyrill Bucher

David Koller

A differential measurement circuit () is implemented in a balance with electromagnetic force compensation. The circuit receives input from two photo currents (I, I) generated by photodiodes (D, D) and generates an output signal proportional to their difference. A switch (SW) controls the flow of current through a node (K) to which the two photo currents are directed, by flipping between two states (z, z) within two phases (t, t) of a time period T. The switch is controlled so a reference current (I) from a voltage or current source (U) is superimposed alternatingly within the time phases on one of the two photo currents which continuously flow into the node. The node lies at the input of an integrator (INT) whose integrator signal (s) can be compared in a comparator (CMP) to a cyclically recurring ramp signal (s) which conforms to the time period. At the output of the comparator, a rectangular-shaped comparator signal (s) can be generated whose duty cycle ratio is defined by the intersection of the integrator signal with the ramp signal and which can be directed to a control input of the switch.

Differential measurement circuit, and balance with force compensation

A force exerted by a load is determined in a force-measuring device () operating under electromagnetic force compensation. The device includes a measurement transducer () with a coil () movably immersed in a magnet system () and a force-transmitting mechanical connection between a load-receiving part () and the coil or magnet system. A position sensor (), also part of the device, determines a displacement of the coil from its settling position relative to the magnet system () which occurs when the load is placed on the load-receiving part. An electrical current () flowing through the coil generates an electromagnetic force between the coil and the magnet system whereby the coil and the load-receiving part are returned to, and/or held at, the settling position. The magnitude of current and the amount of displacement are used to determine the weight force exerted by the load.

Digital linearization in a weighing cell

A force-measuring device () with a parallelogram linkage has a measurement transducer coupled to it. A coil () of the transducer has guided mobility in a magnet system () and can carry an electric current (). A position sensor () detects the deflection of the coil () from a balanced position relative to the magnet system when a load is placed on the force-measuring device. The electric current () flowing through the coil (), by way of the interaction between the coil and the magnet system, returns the coil and the movable parallel leg to the balanced position. A system-characterizing means () is established in a processor unit (). The system-characterizing means and an unchangeable system reference means () are compared to determine the functionality of the device. The functionality is verified by the magnitudes of the electric current and the deflection of the coil from its balanced position.

Diagnostic method for a weighing cell

A method, and a device that is operable according to the method, for monitoring the condition of a force-measuring device, particularly a weighing device having a movable force-transmitting portion through which a force that is acting on the force-measuring device is transmitted to a measurement transducer that generates a measurement signal corresponding to the applied force, whereupon the signal is brought into the form of a display indication or passed along for further processing. In the method and device of the invention, at least one parameter is determined, which parameter characterizes the free mobility of the force-transmitting portion, or a change in the free mobility of the force-transmitting portion over time. The parameter is then compared to at least one threshold value, and based on the result of the comparison an action of the force-measuring device may be triggered.

Method of monitoring the free mobility of a force-measuring device and force-measuring module for applying method

A force measuring device, especially a weighing device, has at least one force-measuring module that includes a force-measuring cell, a communication means, a terminal and at least one communication line, through which communication signals are transmitted between the terminal and the communication means. In a method for determining the condition of such a device, at least one voltage present at the communication line or at the communication means is measured. The measured value, or a processed result therefrom, are transmitted through the communication line to the terminal. A parameter representing the condition of the force-measuring device is determined from the measurement value, or the processed result, in an accurate and simple manner.

Growing community of inventors

Regensdorf, Switzerland

Christoph Trautweiler