Shielded capacitive load cell apparatus responsive to weight applied to a vehicle seat
US7119705B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Oct 30, 2004 |
| Grant date | Oct 10, 2006 |
| Priority date | — |
| Expiry date | Apr 4, 2025 |
Classification
- Technology area (CPC B)Performing Operations; Transporting
- CPC primaryB60N2230/30
- WIPO fieldTransport
- WIPO sectorMechanical engineering
Abstract
The capacitance of a shielded capacitive load cell is determined so as to minimize the effect of stray or parasitic capacitance between the load cell and other objects including the shield. The load cell conductors are coupled across input and output terminals of an operational amplifier that is tied to a reference voltage. A constant current is applied to the load cell, and the resulting rate of change in voltage at the amplifier output is measured as a representation of the load cell capacitance. In a vehicle seat sensor application including an electromagnetic interference shield between the load cell and the seating surface, the amplifier output is coupled to the load cell electrode furthest from the shield, the amplifier maintains the other load cell electrode at a virtual reference voltage, and the shield is tied to the reference voltage.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.