Mettler-toledo Gmbh

David Koller

Hans-Rudolf Burkhard

Andreas Metzger

Christoph Trautweiler

Cyrill Bucher

George Fankhauser

A calibration weight assembly () has at least one calibration weight () and a transfer mechanism, and is used with a gravimetric force-measuring device () having a fixed region (), a load-receiving region (), and a measuring sensor (). The transfer mechanism has at least one poly-stable positioning element (), a first stable state of which defines a calibration position (KP) and a second stable state of which defines a resting position (RP) of the transfer mechanism. The at least one calibration weight can be coupled with the load-receiving region. The transfer mechanism, as actuated by the measuring sensor, transfers the at least one calibration weight from the calibration position to the resting position, or vice versa.

Calibration weight assembly for a gravimetric measuring device

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.

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Zurich, Switzerland

David Koller