US 11,841,249 B2
Capacitive sensing
Robert Money, Fareham (GB); and Peter Timothy Sleeman, Waterlooville (GB)
Assigned to TouchNetix Limited, Farebam/Hampshire (GB)
Appl. No. 16/960,944
Filed by TouchNetix Limited, Fareham (GB)
PCT Filed Nov. 20, 2018, PCT No. PCT/GB2018/053354
§ 371(c)(1), (2) Date Jul. 9, 2020,
PCT Pub. No. WO2019/141958, PCT Pub. Date Jul. 25, 2019.
Claims priority of application No. 1800671 (GB), filed on Jan. 16, 2018.
Prior Publication US 2021/0081073 A1, Mar. 18, 2021
Int. Cl. G01D 5/24 (2006.01); G01D 5/241 (2006.01); G06F 3/041 (2006.01); G06F 3/044 (2006.01)
CPC G01D 5/24 (2013.01) [G01D 5/241 (2013.01); G01D 5/2417 (2013.01); G06F 3/044 (2013.01); G06F 3/0418 (2013.01); G06F 2203/04104 (2013.01)] 15 Claims
OG exemplary drawing
 
1. A displacement sensor comprising:
a first electrode and a second electrode displaceably mounted relative to the first electrode;
capacitance measurement circuitry configured to make measurements of a capacitance associated with the first and second electrodes and to generate analogue capacitance measurement signals in response thereto;
compensation circuitry configured to generate a compensated analogue capacitance measurement signal by reducing a magnitude of a current analogue capacitance measurement signal by an amount indicated by a compensation signal derived from at least one previous analogue capacitance measurement signal; and
processing circuitry configured to digitise the compensated analogue capacitance measurement signal and to determine if there is a displacement of the second electrode relative to the first electrode based on the compensated analogue capacitance measurement signal;
wherein the amount indicated by the compensation signal derived from at least one previous analogue capacitance measurement signal corresponds to a predetermined proportion of the at least one previous analogue capacitance measurement signal, and wherein the predetermined proportion is less than 100% to reduce the chance the compensated analogue capacitance measurement signal will be reduced to below zero,
wherein the compensation circuitry is configured to iteratively adjust the compensation signal for a series of analogue capacitance measurement signals by determining for each one of the series of analogue capacitance measurement signals if the corresponding compensated analogue capacitance measurement signal exceeds a predetermined signal level, and if so increasing the compensation signal for a subsequent one of the series of analogue capacitance measurement signals.