Circuit for measuring capacitance by charging and discharging capacitor under test and its shield
US4743837A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Dec 11, 1986 |
| Grant date | May 10, 1988 |
| Priority date | — |
| Expiry date | Dec 11, 2006 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01B7/14
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A capacitance measuring circuit operating by the principle of switched capacitors includes a switchover device which alternately and periodically with a predetermined switchover frequency connects the measured capacitance for charging to a constant voltage and for discharging to a storage capacitor whose capacitance is large compared with the measured capacitance and whose terminal voltage is held substantially at a constant reference potential by a controlled discharge current. The magnitude of the discharge current is then proportional to the measured capacity and represents the measured value. A further switchover device applies a shield associated with the measured capacitance with the switchover frequency periodically and alternately to potentials which correspond substantially to the constant voltage and reference potential respectively. As a result, the potential of the shield is caused to follow the potential of the electrode to be shielded in accordance with the principle of "active shielding".
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.