GB2121999A

GB2121999A - Electronic weighing machine

Info

Publication number: GB2121999A
Application number: GB08314015A
Authority: GB
Inventors: Erich Knothe; Fran-Josef Melcher; Christian Oldendorf
Original assignee: Sartorius AG
Current assignee: Sartorius AG
Priority date: 1982-06-02
Filing date: 1983-05-20
Publication date: 1984-01-04
Also published as: FR2528171A1; DE3220679C2; CH660083A5; GB2121999B; FR2528171B1; JPS58215516A; GB8314015D0; DE3220679A1

Abstract

In an electronic weighing machine in which a current in a coil 9 is adjusted to balance a weight on a pan 7, pulses from an A/D converter 14 indicative of the weight are fed through an OR gate 15 and counted in a counter 16 during an active interval. In a subsequent quiescent interval clock pulses from a microprocessor 17 are fed through the gate 15 to the counter until this overflows and sets to zero. From the number of these clock pulses and the capacity of the counter the original count and thus the weight can be determined by the microprocessor and displayed. Only two lines join the counter and microprocessor. <IMAGE>

Description

SPECIFICATION Electronic weighing machine The present invention relates to an electronic weighing machine.

In known electronic weighing machines, measurement value pulses are supplied to a counter which is connected by the outputs of individual bistable multivibrators thereof with a microprocessor, through which outputs the microprocessor reads out the state of the counter at the end of the measurement time. In addition, a reset line is present between the microprocessor and counter so that, after reading-out of the counter satting, the counter can be set to zero by the microprocessor. This number of connecting lines is, however, disadvantageous in the case of highly integrated component units.

There is therefore a need for an electronic weighing machine with a simplified connection of the microprocessor to the counter.

According to the present invention there is provided an electronic weighing machine comprising means for providing sequential spaced pulse trains each indicative of a measurement value and for applying the pulses to one input of an OR-gate, a pulse counter connected at input means thereof to the output of the OR-gate to receive and count the pulses of the pulse trains, and a microprocessor which is connected at input means thereof to the counter only at an overflow output of the counter and which is programmed to apply clock pulses to another input of the ORgate during the intervals between the pulse trains.

In a preferred embodiment, the weighing machine comprises a measurement value pick-up which directly or through an analog-to-digital convertor delivers pulse sequences or trains with a pulse number dependent on measurement value, a counter which is acted on by these pulses and a microprocessor for digital signal processing.

Of the outputs of the counter, only the overflow output is connected with the microprocessor, and the microprocessor has a clock output which, during the intervals between the pulse trains, is activatable through the microprocessor program and in the activated state delivers clock pulses.

The clock output of the microprocessor together with the signal output of the measurement value pick-up or of the analog-to-digital convertor is connected through an OR-gate to the input of the counter. For reading-out of the state of the counter, the microprocessor delivers clock pulses until the counter is counted full and the edge of the overflow signal appears. The microprocessor can then determine the original counter state from the number of the clock pulses and the counting capacity of the counter. In this manner of reading out, only two connecting lines are necessary between microprocessor and counter.

An embodiment of the present invention will now be more particularly described by way of example with reference to the accompanying drawing, the single figure of which is a schematic longitudinal sectional view of the principal mechanical parts of an electronic weighing machine embodying the invention, together with a schematic circuit diagram of relevant parts of the electronic system of the machine.

Referring now to the drawing, there is shown an electronic weighing machine, which operates on the basis of electromagnetic force compensation and which comprises a measurement value pick-up consisting of a movable load receiver 3, the receiver 3 carrying a load pan 7 and being connected through two guide rods 5 and 6 in the form of a parallel guide with a stationary part 1 of the weighing machine.

Respective leaf springs 5a, 5b, 6a and 6b at the ends of the guide rods 5 and 6 serve as hinges.

The load receiver 3 is provided at a projecting arm thereof with a coil 9, which stands in reciprocal effect with the field of a stationary permanent magnet system. A position sensor 11 scans the position of the load receiver 3 and delivers, by way of a regulating amplifier 12, the current necessary for the compensation of the loading.

This compensating current is fed through movable feed lines 10 to the coil 9 and at the same time flows through a measuring resistor 13. A measurement voltage proportional to current is taken off across the measuring resistor 1 3 and digitalised in an-analog-to-digital convertor 14.

The digitalisation can in that case take place according to the generally known "dual slope" method or according to the multiple ramp method described in DE 2114 141. Both methods deliver a pulse train, the pulse number of which is proportional to the measurement value, as digitalised measurement result, the pulse trains of successive measurement results being separated from each other through interval times.

The pulses from the convertor 14 are supplied through an OR-gate 1 5 to the input of the counter 1 6 and are counted in the counter. The end of the pulse train and thus the beginning of the interval time is signalled by the convertor 14 through a connecting line 24 to a microprocessor 1 7. In this interval time, the microprocessor 1 7 reads out the state of the counter 1 6 in that the microprocessor delivers, at a clock output 20, clock pulses which are conducted through the second input of the OR-gate 1 5 to the input of the counter. This occurs until the edge of the overflow signal appears at an overflow output 21 of the counter 1 6. The microprocessor 1 7 stops the delivery of the clock pulses at its clock output 20 so that the counter 16 remains at zero and is ready for counting of the next pulse train. The microprocessor 1 7 can then determine the original state of the counter 1 6 from the counting capacity of the counter 1 6 and the number of the clock pulses which the microprocessor has delivered up to the appearance of the overflow signal.

This digital measurement result is processed further (taring, arithmetical conversion to predetermined weight units and so forth) in the microprocessor 1 7 and indicated in a digital indicating unit 18.

Claims

1. An electronic weighing machine comprising means for providing sequential spaced pulse trains each indicative of a measurement value and for applying the pulses to one input of an OR-gate, a pulse counter connected at input means thereof to the output of the OR-gate to receive and count the pulses of the pulse trains, and a microprocessor which is connected at input means thereof to the counter only at an overflow output of the counter and which is programmed to apply clock pulses to another input of the ORgate during the intervals between the pulse trains.

2. A weighing machine as claimed in claim 1, the means for providing and applying the pulse trains comprising an analog-to-digital convertor connected at output means thereof to said one input of the OR-gate.

3. A weighing machine as claimed in either claim 1 or claim 2, wherein the microprocessor is programmed to terminate application of clock pulses to the OR-gate on appearance of an overflow signal at the overflow output of the counter.

4. A weighing machine as claimed in any one of the preceding claims, wherein the microprocessor is arranged to calculate the number of pulses in each pulse train from the counting capacity of the counter and from the number of clock pulses appiied to the OR-gate in the interval immediately following that pulse train.

5. A weighing machine as claimed in any one of the preceding claims, wherein the microprocessor is programmed to initiate application of clock pulses to the OR-gate on receipt of a signal directly from the means for providing and applying the pulse trains.

6. An electronic weighing machine substantially as hereinbefore described with reference to the accompanying drawing.