Weighing device and method with off-center indication

Patent metadata

Field	Value
Publication number	US-9939309-B2
Application number	US-201314415704-A
Country	US
Kind code	B2
Filing date	Jul 19, 2013
Priority date	Jul 19, 2012
Publication date	Apr 10, 2018
Grant date	Apr 10, 2018

Abstract

Electronic scale including four feet, four strain gauges, an electronic control unit and a display, where the gauges are combined in pairs in first and second Wheatstone bridge type circuits, where a first intermediate-point of the bridge is selectively connected via a switch to an intermediate voltage source and where the first and second outputs of the amplifiers are summed by the electronic control unit in order to deduce therefrom a weight for an object present on the device, with indication for the user of off-center condition on the scale. Weighing method implemented in such a scale.

First claim

The invention claimed is:

1. A weighing device, including four feet, respectively, left front, right front, left rear and right rear, where the left-front foot includes a left-front strain gauge, the right-front foot includes a right-front strain gauge, the left-rear foot includes a left-rear strain gauge and the right-rear foot includes a right-rear strain gauge; the weighing device furthermore includes an electronic control unit,
where the right-front and right-rear strain gauges are combined in a first circuit with a first Wheatstone bridge and a first amplifier, with a first output representative of a weight sensed at right side, and the left-front and left-rear strain gauges are arranged in a second circuit with a second Wheatstone bridge and a second amplifier, with a second output representative of a weight sensed at left side, and wherein the first and second outputs are connected to the electronic control unit to be digitized and added and for thus deducing therefrom the total weight of an object present on the device, and wherein the first and second outputs are compared to indicate a possible left-right off center stance on a display,

in which each Wheatstone bridge type circuit includes a first branch comprising two front gauge resistors arranged in series between a reference voltage and a ground potential with a first intermediate point between the two front gauge resistors, and a second branch comprising two rear gauge resistors arranged in series between the reference voltage and the ground potential with a second intermediate point between the two rear gauge resistors, where the first and second intermediate points are connected to the corresponding amplifier, and where one of the first or second into points can furthermore be selectively connected to an activable intermediate voltage source such that when the activable intermediate voltage source is activated, the voltage difference measured between the first and second intermediate points is representative of a front-rear imbalance.

2. The weighing device according to claim 1 , in which the electronic control unit is configured for displaying on the display at least one indication for the user of an off-center condition on the scale.

3. The weighing device according to claim 1 , in which the two front gauge resistors of each Wheatstone bridge type circuit include a front-gauge first resistor arranged between the ground potential and the first intermediate point and a front-gauge second resistor arranged between the first intermediate point and the reference voltage, and in which the two rear gauge resistors of each Wheatstone bridge type circuit include a rear-gauge first resistor arranged between the ground potential and the second intermediate point and a rear-gauge second resistor arranged between the second intermediate point and the reference voltage,
where the front-gauge first resistor and the rear-gauge first resistor increase with the load whereas the front-gauge second resistor and the rear-gauge second resistor decrease with the load.

4. The weighing device according to claim 1 , in which the display includes four corner arrows corresponding respectively to the four feet of the device, where one of the four arrows can be displayed in case of being substantially off-center towards one corner.

5. The weighing device according to claim 1 , in which the intermediate voltage is half of the reference voltage.

6. A method implemented in a weighing, device comprising four strain gauges, an electronic control unit, where the right-front and right-rear strain gauges are combined in a first Wheatstone bridge type circuit with a first output coming from a first amplifier and the left-front and left-rear strain gauges are arranged in a second Wheatstone bridge type circuit with a second output coming from a second amplifier,
each Wheatstone bridge type circuit including a first branch comprising two front gauge resistors in series between a reference voltage and a ground potential with a first intermediate point between the two resistors,
and a second branch comprising two rear gauge resistors arranged in series between the reference voltage and the ground potential with a second intermediate point between the two resistors, where the first and second intermediate points are connected to said amplifier, and where one of the first and/or second intermediate points can be selectively connected to an intermediate voltage source,

the method comprising the steps:
a- a calibration step during which a first series of parameters is recorded for a plurality of reference weights placed successively on the weighing device with the first and second intermediate points not coupled to the intermediate voltage source, and a second series of parameters for the plurality of reference weights placed successively on the weighing device with one of the first and/or second intermediate points coupled to the intermediate voltage source;
b1- a weighing step during which the first and second outputs are measured with the first, and second intermediate points not coupled to the intermediate voltage source and the resulting digitized total corrected by means of the first series of parameters, in order to obtain an estimated weight;
b2- an off-center evaluation step during which one of the first and/or second intermediate points coupled to the intermediate voltage source and the digitized total from the first and second outputs is compared to a point from the second series, of parameters corresponding to the estimated weight, in order to identify an off-center condition and indicate it to the user;
c- steps b1- and b2- are repeated.

7. The method according to claim 6 , additionally comprising:
d- a final step during which the iteration of steps b1- and b2- is stopped when the evaluation of an off-center distance is less than a preset threshold during at least a preset time and then the resulting estimated weight is displayed on a display.

8. The method according to claim 7 , in which the display comprises corner arrows and in which a left-right off-center condition is identified by comparing the first and second outputs from step b1- and a front-rear off-center condition is identified by comparing the total of the first and second outputs to the second series of parameters in step b2- in order to determine whether it is necessary to display a corner arrow corresponding to the more heavily loaded strain gauge.

9. The method according to claim 7 , in which the user selects an element on the display by standing intentionally off-center left-right.

10. The method according to claim 7 , in which the measured weight is displayed on the display as a function of the total of the first and second outputs corrected by means of the first series of parameters.

11. The method according to claim 6 , additionally comprising:
b0- a taring step during which a tare measurement is done with no object placed on the device and a subsequent weight measurement is compensated by an offset corresponding to the tare weight.

12. A weighing device, including four feet, respectively, left front, right front, left rear and right rear, where the left-front foot includes a left-front strain gauge, the right-front foot includes aright-front strain gauge, the left-rear loot includes a left-rear strain gauge and the right-rear foot includes a right-rear strain gauge; the weighing device furthermore includes an electronic control unit,
where the right-front and left-front strain gauges are combined in a first circuit with a first Wheatstone bridge and a first amplifier, with a first output representative of a weight sensed at front

Assignees

• Withings

Inventors

• Carreel Eric
• Buard Nadine
• Debreuil Xavier
• Ting Victor
• Campo David
• Faussard Guillaume
• Dusanter Florent

Classifications

• G01G3/1402 Primary

  Special supports with preselected places to mount the resistance strain gauges; Mounting of supports · CPC title

• G01G19/44

  for weighing persons · CPC title

• G01G3/1404 Primary

  combined with means to connect the strain gauges on electrical bridges · CPC title