Patent ID: 8854057
Filing Date: 2014-10-07
Classification: G01D,G01P,G01R,H01L,Y10T

Abstract:
1. A capacitive sensor system resistant to electromagnetic interference, the capacitive sensor system comprising: a capacitive core including a first variable capacitor, a second variable capacitor, a first core output coupled to the first variable capacitor, a second core output coupled to the second variable capacitor, and a common node coupling the first variable capacitor and the second variable capacitor; a differential amplifier including an inverting input and a non-inverting input; a first capacitive path between the first core output and the inputs of the differential amplifier; a second capacitive path between the second core output and the inputs of the differential amplifier; a chopping system having a high state and a low state, the chopping system coupling the first and second core outputs to the inputs of the differential amplifier, wherein when the chopping system is in the high state, a positive step voltage is applied to the common node of the capacitive core, and the chopping system couples the first core output to the inverting input of the differential amplifier and couples the second core output to the non-inverting input of the differential amplifier; and when the chopping system is in the low state, a negative step voltage is applied to the common node of the capacitive core, and the chopping system couples the first core output to the non-inverting input of the differential amplifier and couples the second core output to the inverting input of the differential amplifier.