Capacitive sensor

An improved two loop capacitive sensor oscillator circuit to convert a transducer capacitance to frequency comprising:

• a first loop means for creating an oscillatory waveform having a frequency related to a capacitance of the capacitive transducer, the first loop means including a resistor having a resistor first connection and a resistor second connection, the resistor second connection electrically coupled to a capacitor (Cs1), having a capacitor (Cs1) first connection and a capacitor (Cs1) second connection, the resistor second connection electrically coupled to the capacitor (Cs1) first connection and the capacitor (Cs1) second connection electrically coupled to an electrical common, the resistor second connection also electrically coupled to the capacitive transducer, the capacitive transducer having a capacitive transducer first connection and a capacitive transducer second connection, the resistor second connection electrically coupled to the capacitive transducer first connection, the capacitive transducer second connection electrically coupled to an input of a first inverter gate also having a first inverter gate output, the first inverter gate output electrically coupled to a second inverter gate input, the second inverter gate also having a second inverter gate output, and the second inverter gate output electrically coupled to the resistor first connection, closing the first loop means, the first and second inverter gates powered by a source of power (Vcc);
• and
• a second loop means for generating a second waveform of a substantially square wave shape having the same frequency and oscillating at the frequency of the first loop means, the second loop means electrically coupled to the first loop means, the second loop means including an input to the second loop means 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 means, the third inverter gate also powered by the source of power (Vcc), wherein the second loop means is electrically coupled to the first loop means and the output of the third inverter gate is the substantially square wave at the frequency related to the capacitance of the capacitive transducer.

An improved two loop capacitive sensor oscillator circuit to convert a transducer capacitance to frequency comprising:

• an oscillator having two loops including a first loop to create a saw tooth waveform having a frequency inversely proportional to a capacitance value of the capacitive transducer, and a second loop electrically coupled to the first loop, the first loop including a resistor and a capacitance to form an RC low pass filter to reduce RF interference and to limit the voltage of the waveform as applied to an input of a gate in the first loop and the capacitive transducer, the second loop comprising a gate and a resistor, wherein both the gate and the resistor of the second loop are coupled to the first loop, the input of the gate in the second loop connected to an output of the gate in the first loop and the resistor of the second loop connected to the input of the gate in the first loop, the second loop further providing a substantially squared output waveform at the oscillator frequency at the output of a gate in the second loop, the gates of both the first loop and the second loop powered by a source of power (Vcc) referenced to an electrical common, wherein the low pass filtered saw tooth waveform has a maximum voltage and a minimum voltage and the minimum voltage is greater than or equal to electrical common and the maximum voltage is less than or equal to Vcc.