Weighing device having inductive sensing elements

Patent metadata

Field	Value
Publication number	US-9759599-B2
Application number	US-201514739868-A
Country	US
Kind code	B2
Filing date	Jun 15, 2015
Priority date	Jun 15, 2015
Publication date	Sep 12, 2017
Grant date	Sep 12, 2017

Abstract

A thin personal weighing device comprising a bottom plate, extending along a reference plane, a top plate movably mounted with regard to the bottom plate along a direction perpendicular to the reference plane, four resilient elements directly interposed between the top and the bottom plate, four LC circuits positioned at a vicinity of an edge of the bottom plate, and a conductive material coating, arranged on the top plate, the four LC resonators and the at least conductive material coating exhibiting an inductance. Movement of the conductive material coating relative to each of the four LC resonators introduces a variation of the inductance. A computation unit detecting the variations of the inductance is electronically coupled with the LC resonators and configured to correlate the variations of the inductance with an actual weight placed on the weighing device. The thickness of the weighing device is less than 25 mm.

First claim

The invention claimed is:

1. A thin personal weighing device comprising:
a bottom plate, extending along a reference plane,
a top plate, movably mounted with regard to the bottom plate, at least along a third direction perpendicular to the reference plane,
at least four resilient elements, each directly interposed between the top plate and the bottom plate, and
at least four LC circuits each positioned at a vicinity of an edge of one of the top plate or the bottom plate,
at least a conductive material coating, arranged on the other of the top plate or the bottom plate, the four LC circuits and the at least conductive material coating exhibiting an inductance,
wherein during operation of the weighing device a movement of the at least conductive material coating relative to each of the at least four LC circuits along the third direction introduces a variation of the inductance,
wherein the weighing device further comprises a computation unit electronically coupled with the LC circuits and programmed to detect the variations of the inductance, and
wherein the computation unit is configured to correlate the variations of the inductance with an actual weight placed on the weighing device, and
wherein the thickness of the weighing device is less than 25 mm.

2. The weighing device according to claim 1 comprising exactly four LC circuits, wherein positions of the four LC circuits form a rectangle.

3. The weighing device according to claim 2 , wherein the at least one of the top plate and the bottom plate has a rectangular shape, such that each of the four LC circuits is positioned at one of the corners of one of the top plate and the bottom plate.

4. The weighing device according to claim 2 comprising exactly four resilient elements, wherein each of the four resilient elements occupies one of four quadrants of the rectangle defined by the positions of the four LC circuits.

5. The weighing device according to claim 1 , wherein the number of the at least four resilient elements is the same as the number of the at least four LC circuits, and wherein the at least four resilient elements and the at least four LC circuits are arranged in pairs.

6. The weighing device according to claim 5 , wherein the at least four resilient elements are in form of a diaphragm spring or an annular spring.

7. The weighing device according to claim 6 , wherein each of the at least four LC circuits is arranged in the middle of the corresponding diaphragm spring or annular spring.

8. The weighing device according to claim 5 , wherein the computation unit comprises a plurality of sets of calibration parameters, such that each set of calibration parameters is allocated to one pair of the resilient element and the LC circuit.

9. The weighing device according to claim 1 , wherein the at least four LC circuits are positioned on the bottom plate, and where the at least conductive material coating is formed by at least a layer of the top plate.

10. The weighing device according to claim 9 , comprising a ferrite layer at the back of each of the at least four LC circuits.

11. The weighing device according to claim 1 , wherein the thickness of the weighing device is less than 20 mm.

12. The thin personal weighing device according to claim 1 , wherein the changes in distance between the at least conductive material coating and each of the at least four LC circuits are smaller than or equal to 2 mm.

13. A method of calibration of a personal weighing device comprising:
placing a reference weight in the centre and successively over each position of at least four LC circuits at a vicinity of an edge of a top plate of the weighing device,
acquiring calibration data from each of the at least four LC circuits and for each position of the reference weight in a computation unit, and
storing the calibration data in the computation unit, so that the actual weight measured with the weighing device is determined based on the stored calibration data.

Assignees

• Withings

Inventors

• Bedetti Thomas
• Joussain Antoine
• Carreel Eric

Classifications

• G01G23/01

  Testing or calibrating of weighing apparatus · CPC title

• G01G7/00

  Weighing apparatus wherein the balancing is effected by magnetic, electromagnetic, or electrostatic action, or by means not provided for in the preceding groups · CPC title

• G01G23/00

  Auxiliary devices for weighing apparatus · CPC title

• G01G19/44 Primary

  for weighing persons · CPC title