Mettler Instrumente Ag

Mettler Instruments Ag

Arthur Baumann

Rudolf Bachmann

Christian Liechti

The calibration process is initialized as a function of the past measurement results. The time to the next calibration is dependent on the quality of the calibrations in the past. Before the calibrating of the balance, the program checks a number of parameters, which can affect the weighing result and compares the results with predetermined limits. If set conditions are exceeded, the program in each case returns to the beginning and starts anew.

Method for the automatic calibration of a high-resolution electronic

The invention relates to a circuit and a method adapted for measuring and digitizing the value of a resistance. The circuit includes and A/D converter operating in accordance with a charge balancing principle, and a resistance network connected to the A/D converter so that the resistance is both a component of the A/D converter and of the resistance network. The A/D converter and the resistance network are interconnected in such a manner so as to permit only a purely resistive measurement. A processor is connected to the A/D converter for obtaining a composite measured resistance value from a plurality of individual measured resistance values. The method according to the invention permits accurate (or precise) resistance measurements having a high degree of resolution of an order of magnitude of 10.sup.5 points. The method is applicable in particular for temperature measurements, for examples in calorimeters or in precision scales, but also in other resistance measurements.

Circuit and method for measuring and digitizing the value of a resistance

Weighing apparatus of the electromagnetic load compensation type includes an improved variable (C.sub.x) and reference (C.sub.o) capacitance comparison arrangement for sensing the position of the movable load receiver member relative to the stationary base member. The comparison arrangement supplies an error signal that is proportional to the capacity ratio, which error is used to control a compensation current (i.sub.L) that is supplied to a compensation coil to maintain the movable load receiver member at its initial zero position. The variable capacitance is produced by a variable air capacitor including a first pair of stationary capacitor plate electrodes (10, 12), and a movable plate-like metal shield or screen which extends partially between the first pair of electrodes in accordance with movement of the load receiver member. The position sensor arrangement is simple to construct and install, and affords precise measurement during use. All of the plate-like capacitor electrodes are stationary, and can be mounted in the immediate vicinity of the error signal generator.

Capacitive position sensing means for weighing apparatus of the

Display for an electronic weighing scale

To start a metering process, the operator enters the desired weight value into a display control. The display contains a container shaped figure which is 'filled' as material is added to the balance. The rate at which the container fills relative to the rate at which the substance is being applied to the instrument changes during the metering process. It is slow during the coarse starting phase and more rapid during the final fine metering phase. The shape of the bottle preferably corresponds to the 'fill' rate, i.e. it is relatively wide at the bottom and has a narrow neck at the top. The display is controlled by a microcomputer.

Apparatus and method for generating a pictorial display on a measuring

An optical display is provided to guide the operator during metering of a substance to a desired value. The desired value is entered into a computer and the substance to be metered is applied to a balance. The display is in the form of a clock having a coarse and fine indicator hand. During the coarse metering at the start of the metering cycle, the coarse metering hand is rotated at a first rotational speed relative to the metering rate, i.e. the rate at which the substance is being applied to the balance. During the fine metering phase, namely when the weight on the balance approaches the desired weight, either the same or another hand moves at a rotational speed relative to the metering rate which exceeds the first rotational speed, thereby expanding the sector over which the hand moves while a given amount of the substance is being applied. This greatly facilitates the operator's control over the process and decreases the possibilities that excess weight is added.

Balance with clock-like display

An automatic monitoring system for the constant current source in a balance having electromagnetic load compensation includes circuitry which generates a first current varying in dependence on the constant current and furnishes a digital signal indicative of the value of that current. A microcomputer is provided to compare the digital value to a reference value. If the comparison indicates that the constant current is outside of a given range of values, the microcomputer energizes the display to indicate the presence of an error.

Apparatus for automatically monitoring a constant current source in a

The multi-segment indicator can be selectively switched to operate as a range display. For this purpose, the vertical segments are deactivated. Each digit in the multi-segment indicator has a top, bottom and middle horizontal segment. If the measured value is, respectively, less than equal to or greater than a desired value, all bottom, middle, and top segments, respectively are activated. Alternatively, all middle segments are activated if the measured value is within a desired range, the top and bottom segments being activated if the measured value is, respectively, greater than the upper limit of the range or less than the lower limit of the range. The sign of the measured, desired, and limiting values is considered before activation of the corresponding horizontal segments.

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Bertschikon, Switzerland

Arthur Baumann