LOAD CELL FOR SMART CAP
A weight sensor assembly including a strain gauge load cell is disclosed. The weight sensor assembly may be used in a smart cap. The weight sensor includes a platform for weighing objects and a load cell. The load cell includes an annular portion, and first and second beams coupled to the platform. Each of the beams includes a first end fixed to the annular portion and a second end that deforms as the platform displaces downward in response to an applied force. One or more strain gauges are mounted on the beams.
1 . A weight sensor assembly, comprising:
a platform; and
a load cell, comprising:
an annular portion;
a first beam and a second beam coupled to the platform, wherein each of the beams comprises:
a first end fixed to the annular portion; and
a second end that deforms as the platform displaces downward in response to an applied force; and
a first strain gauge mounted on the first beam and a second strain gauge mounted on the second beam.
2 . The weight sensor assembly of claim 1 , wherein the diameter of the load cell is less than 45 millimeters.
3 . The weight sensor assembly of claim 2 , wherein the diameter of the load cell is at least 100 times greater than the thickness of the load cell.
4 . The weight sensor assembly of claim 2 , wherein the diameter of the load cell is at least 100 times greater than the thickness of the beams of the load cell.
5 . The weight sensor assembly of claim 4 , wherein each of the first beam and the second beam is between 0.2 and 0.3 millimeters thick and between 3.5 and 5.5 millimeters wide.
6 . The weight sensor assembly of claim 2 , further comprising: a third strain gauge mounted on the first beam on a surface opposite the first strain gauge, and a fourth strain gauge mounted on the second beam on a surface opposite the second strain gauge.
7 . The weight sensor assembly of claim 2 , further comprising: a support ring, wherein the annular portion is directly coupled to the support ring.
8 . The weight sensor of claim 2 , further comprising: a center connecting beam, the center connecting beam, comprising:
a first end coupled to the second end of the first beam; and
a second end coupled to the second end of the second beam,
wherein the center connecting beam keeps the distance between the first beam and the second beam fixed as the first beam and the second beam deform as the platform displaces downward.
9 . A load cell for a strain gauge weight sensor, the load cell comprising:
an annular portion;
a first beam and a second beam extending inward from the annular portion, wherein each of the beams comprises:
a first end fixed to the annular portion; and
a second end that deforms in response to a load force applied to the beams.
10 . The load cell claim 9 , wherein the diameter of the load cell is less than 45 millimeters.
11 . The load cell of claim 10 , wherein the diameter of the load cell is at least 100 times greater than the thickness of the load cell.
12 . The load cell of claim 10 , wherein the diameter of the load cell is at least 100 times greater than the thickness of the beams of the load cell.
13 . The load cell of claim 12 , wherein each of the first beam and the second beam is between 0.2 and 0.3 millimeters thick and between 3.5 and 5.5 millimeters wide.
14 . The load cell of claim 10 , wherein the first beam and the second beam each comprise apertures for directly coupling the beam to a platform of a weight sensor.
15 . The load cell of claim 14 , further comprising: a center connecting beam, the center connecting beam, comprising:
a first end coupled to the second end of the first beam; and
a second end coupled to the second end of the second beam,
wherein the center connecting beam keeps the distance between the first beam and the second beam fixed as the first beam and the second beam deform in response to a load force applied to the beams.
16 . The load cell of claim 10 , wherein each of the first and second beams is at least 100 times stiffer in the off-axis direction relative to the on-axis direction.
17 . A cap, comprising:
a circuit board;
a weight sensor assembly, comprising:
a platform; and
a load cell, comprising:
an annular portion;
a beam coupled to the platform, wherein the beam comprises a first end fixed to the annular portion and a second end that deforms as the platform displaces downward in response to an applied force; and
a strain gauge mounted on the beam, wherein the strain gauge is electrically coupled to the circuit board.
18 . The cap of claim 17 , wherein the load cell further comprises: a second beam coupled to the platform, wherein the second beam comprises a first end fixed to the annular portion and a second end that deforms as the platform displaces downward in response to an applied force.
19 . The cap of claim 18 , wherein the weight sensor assembly further comprises a second strain gauge mounted on the second beam, wherein the second strain gauge is electrically coupled to the circuit board.
20 . The cap of claim 17 , further comprising: an enclosure, wherein the enclosure houses the circuit board and the weight sensor assembly.