Capacitance change detection device
US7098675B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Mar 24, 2005 |
| Grant date | Aug 29, 2006 |
| Priority date | — |
| Expiry date | Mar 24, 2025 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH03K2217/94031
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A capacitance change detection device includes a sensor electrode, and an electrode capacitance measurement device for measuring capacitance of the sensor electrode on the basis of a correlation value based on a reference capacitance at every first predetermined time. A detection signal is generated when a current measurement value of capacitance is changed by equal to or greater predetermined threshold value than a measurement value obtained a second predetermined time before the current measurement value is measured. The capacitance change detection device further includes a sensitivity compensation capacitance for generating capacitance variations equivalent to specific variations of capacitance of the sensor electrode, and being switched between a connected state and a disconnected state. The threshold value is determined as a difference between measurement values of capacitance of the sensor electrode measured at the connected state and at the disconnected state. The threshold value is renewed at every third predetermined time.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.