Patent ID: 7119551
Filing Date: 2006-10-10
Classification: G01D,G01L

Abstract:
1. An improved two loop capacitive sensor oscillator circuit to convert a transducer capacitance to frequency comprising: a first loop to create an oscillatory waveform having a frequency related to a capacitance of the capacitive transducer, the first loop including a resistor having a resistor first connection and a resistor second connection, the resistor second connection electrically coupled to a capacitor (Cs a second loop oscillating at the frequency of the first loop and to further generate a second waveform of a substantially square wave shape having the same frequency, the second loop electrically coupled to the first loop, the second loop including an input to the second loop being the input of a third inverter gate also having a third inverter gate output, the third inverter gate input electrically coupled to the second inverter gate output, the third inverter gate output electrically coupled to a second loop resistor first connection, the second loop resistor also having a second loop resistor second connection, the second loop resistor second connection electrically coupled to the input of the first inverter gate, closing the second loop, the third inverter gate also powered by the source of power (Vcc), wherein the second loop is electrically coupled to the first loop and the output of the third inverter gate is the substantially square wave at the frequency related to the capacitance of the capacitive transducer.