Patent ID: 7119705
Filing Date: 2006-10-10
Classification: B60N,G01L

Abstract:
1. Apparatus for measuring a weight applied to a seating surface of a vehicle seat, comprising: a load cell disposed in said seat including first and second conductive plates separated by a compressible insulator; a conductive shield disposed between said seating surface and said load cell; and circuitry coupled to said load cell and said conductive shield, including means for maintaining said shield at a reference voltage, an operational amplifier having a first input coupled to said first conductive plate and an output coupled to said second conductive plate, current supply elements for supplying a constant current to said load cell, and means for determining a capacitance of said load cell based on a rate of change in voltage at the output of said operational amplifier, said capacitance providing an indication of the weight applied to said seating surface.