Apparatus and method of calibrating of a force sensing device by establishing an optimized force-resistance curve

1. A method of calibrating a force sensing device, comprising the steps of:

measuring first calibration data for a set of substantially similar force sensing devices;

deriving a plurality of force-resistance curves from said first calibration data, each one of said plurality of force-resistance curves corresponding to one force sensing device in said set of substantially similar force sensing devices;

establishing an optimized force-resistance curve by obtaining a mean resistance of said plurality of force-resistance curves;

measuring second calibration data of said force sensing device;

defining a plurality of calibration points from said second calibration data;

applying said plurality of calibration points to said optimized force-resistance curve;

adapting said optimized force-resistance curve to form an adapted force-resistance curve by interpolating said plurality of calibration points and determining a multiplier value for each calibration point of said plurality of calibration points; and

calibrating said force sensing device from said adapted force-resistance curve.

2. The method of claim 1 , wherein said plurality of calibration points is three or more.

3. The method of claim 1 , wherein said plurality of calibration points is four.

4. The method of claim 1 , wherein said method provides a maximum force error of twenty-five percent.

5. The method of claim 1 , further comprising the step of:

applying a preload to an electronic device comprising said force sensing device.

6. The method of claim 1 , wherein said force sensing device comprises a first conductive layer, a second conductive layer, and a pressure sensitive layer positioned between said first conductive layer and said second conductive layer.

7. The method of claim 6 , wherein said pressure sensitive layer comprises a quantum tunnelling material.

8. The method of claim 1 , wherein said plurality of calibration points adapt said optimized force-resistance curve by gradient, curvature, or offset of said optimized force-resistance curve such that said plurality of calibration points are in close proximity to a measured force sensing device data force-resistance curve.

9. The method of claim 1 , wherein said step of adapting comprises:

measuring a resistance in said force sensing device at a plurality of predetermined forces to determine an actual force-resistance curve for said force sensing device; and

recording a difference between said optimized force-resistance curve and said actual force-resistance curve.

10. The method of claim 1 , wherein said method utilizes Piecewise Cubic Hermite Interpolating Polynomial (PCHIP) to adapt said optimized force-resistance curve into said adapted force-resistance curve.

11. The method of claim 1 , further comprising the steps of:

measuring a resistance from said force sensing device when no force is applied;

comparing said measured resistance with a predetermined zero force-resistance measurement; and

providing further adaptation of said optimized force-resistance curve to account for a difference between said measured resistance and said predetermined zero force-resistance measurement.

12. Apparatus for measuring a mechanical interaction, comprising:

a force sensing device comprising a first conductive layer, a second conductive layer, and a pressure sensitive layer between said first conductive layer and said second conductive layer; and

a processor configured to:

measure first calibration data for a set of substantially similar force sensing devices;

derive a plurality of force-resistance curves from said first calibration data, each one of said plurality of force-resistance curves corresponding to one force sensing device in said set of substantially similar force sensing devices;

establish an optimized force-resistance curve by obtaining a mean resistance of said plurality of force-resistance curves;

measure second calibration data of said force sensing device;

define a plurality of calibration points from said second calibration data;

apply said plurality of calibration points to said optimized force-resistance curve;

adapt said optimized force-resistance curve to form an adapted force-resistance curve by interpolating said plurality of calibration points and determining a multiplier value for each calibration point of said plurality of calibration points; and

calibrate said force sensing device from said adapted force-resistance curve.

13. The apparatus of claim 12 , wherein said pressure sensitive layer comprises a quantum tunnelling material.

14. The apparatus of claim 12 , wherein said apparatus is incorporated into an electronic device.

15. The apparatus of claim 14 , wherein said electronic device comprises a touch screen.