Methods and apparatus for a capacitive sensor

A capacitive sensor, comprising:

• a detection circuit configured to detect a change in capacitance;
• and
• a sensing element connected to the detection circuit, comprising:
• a first electrode and a second electrode, wherein the first and second electrodes form a sensing capacitor;
• a reference capacitor, wherein the reference capacitor has a fixed capacitance;
• a first external capacitor connected in series with the sensing capacitor;
• a first node, located between the first external capacitor and the sensing capacitor, connected to the detection circuit;
• a second external capacitor connected in series with the reference capacitor;
• and
• a second node, located between the second external capacitor and the reference capacitor, connected to the detection circuit.

A capacitive sensor, comprising:

• a detection circuit configured to detect a change in capacitance;
• wherein the detection circuit comprises a first multiplexer, wherein the first multiplexer comprises a plurality of input terminals;
• and
• a sensing element connected to the detection circuit, comprising:
• a first sensing capacitor, wherein the first sensing capacitor is connected to a first input terminal from the plurality of input terminals of the multiplexer;
• a second sensing capacitor, wherein the second sensing capacitor is connected to a second input terminal from the plurality of input terminals of the multiplexer;
• a reference capacitor connected to the first and second sensing capacitors, wherein the reference capacitor has a fixed capacitance;
• a first external capacitor connected to a third input terminal from the plurality of input terminals of the first multiplexer;
• and
• a second external capacitor connected in series with the reference capacitor.