Patent ID: 8531193
Filing Date: 2013-09-10
Classification: G01D,G08B,H03K

Abstract:
1. A device for capacitively detecting an object, said device comprising: a capacitive sensor having a sensor capacitor formed between at least one first capacitive element and at least one second capacitive element such that a presence of said object can change a capacitance of said sensor capacitor, a voltage supply, a first switch to couple said sensor capacitor to said voltage supply in order to charge said sensor capacitor, a tank capacitor having an adjustable capacitance, a second switch to couple said sensor capacitor to said tank capacitor in order to transfer charge from said sensor capacitor to said tank capacitor and to change the voltage of said tank capacitor, at least one switch driver unit to control said charging and charge transfer by opening and closing said switches several times such that said switches are not in the closed state simultaneously, a voltage monitoring unit to monitor the voltage of said tank capacitor, and a controller to determine at least one measurement value which depends on the rate of change of the voltage of said tank capacitor, wherein said controller is arranged to count a number of consecutive closing cycles of said second switch needed for an average of several measured values of the voltage of said tank capacitor to reach or exceed a predetermined voltage level.