Proximity sensor with reduced temperature sensitivity using A.C. and D.C. energy

A proximity sensor, comprising:

• first means for providing a DC voltage;
• second means for providing an AC voltage;
• means for summing said AC and DC voltages to form a combined voltage, said summing means being connected in electrical communication with said first and second providing means;
• means for driving a current through a coil of said sensor, said current being a function of said combined voltage;
• first means for measuring a DC voltage potential across said coil, said driving means and first measuring means being connected in electrical communication with said coil;
• second means for measuring an AC voltage potential across said coil, said first and second measuring means being connected in electrical communication with said coil;
• first means for determining a DC resistance of said coil as a function of said DC voltage potential;
• second means for determining an AC impedance of said coil as a function of said AC voltage potential;
• and
• means for deriving, connected in signal communication with said first and second determining means, a discriminator value magnitude as a function of said AC impedance and said DC resistance.

A method of operating a proximity sensor, comprising:

• providing a DC voltage;
• providing an AC voltage;
• summing said AC and DC voltages to form a combined voltage;
• driving a current through a coil of said sensor, said current being a function of said combined voltage;
• measuring a DC voltage potential across said coil;
• measuring an AC impedance potential across said coil;
• determining a DC resistance of said coil as a function of said DC voltage potential;
• determining an AC impedance of said coil as a function of said AC voltage potential;
• and
• deriving a discriminator value magnitude as a function of said AC impedance and said DC resistance.