Three wire transformer position sensor, signal processing circuitry, and temperature compensation circuitry therefor

A position sensor, comprising:

• an excitation coil adapted to be electrically excited with an excitation signal, the output coil having a first end and a second end;
• an output coil inductively coupled to the excitation coil upon electrical excitation of the excitation coil and configured, when it is balanced and the excitation coil is being electrically excited, to supply a null output signal, the output coil including a first coil and a second coil, the first coil having a first end and a second end, the second coil having a first end and a second end;
• and
• a core disposed adjacent, and movable relative to, the excitation coil and the output coil, the core operable, upon movement thereof, to vary inductive coupling between the excitation coil and the output coil,
• wherein:
• the first end of the first coil is electrically connected to the second end of the second coil and to the second end of the excitation coil, to thereby define a common node,
• the second end of the first coil is electrically connected to the first end of the second coil, to thereby define a signal output node, and
• the first end of the excitation coil defines an excitation node.

A position sensor, comprising:

• an excitation coil coupled to receive an excitation signal, the excitation coil having a first end a second end;
• inductively coupled to the excitation coil upon electrical excitation of the excitation coil and configured, when it is balanced and the excitation coil is being electrically excited, to supply a null output signal, the output coil including a first coil and a second coil, the first coil having a first end and a second end, the second coil having a first end and a second end;
• a core disposed adjacent, and movable relative to, the excitation coil and the output coil, the core operable, upon movement thereof, to vary inductive coupling between the excitation coil and the output coil;
• a constant current circuit coupled to the excitation coil, the constant current circuit configured to supply a constant direct current (DC) to the excitation coil;
• a filter circuit coupled to the excitation coil to receive a voltage signal representative of a voltage drop across the excitation coil and configured, upon receipt thereof, to supply a temperature signal having a voltage amplitude magnitude that is proportional to excitation coil temperature;
• a plurality of resistors, each of the resistors having a first terminal and a second terminal and a resistance value unequal to another one of the resistors, the first terminal of each resistor adapted to receive a voltage from an electric power source;
• and
• a processor having a plurality of pins, each of the pins individually coupled to the second terminal of one of the resistors, the processor configured to:
• (i) selectively draw current from the electric power source through each of the resistors to thereby generate and supply a stair-step sinusoidal excitation voltage for the excitation coil, (ii) receive an output signal from the output coil, and (iii) upon receipt of the output signal, supply a position signal representative of relative core position,
• wherein:
• the first end of the first coil is electrically connected to the second end of the second coil and to the second end of the excitation coil, to thereby define an electrical common node,
• the second end of the first coil is electrically connected to the first end of the second coil, to thereby define a signal output node, and
• the first end of the excitation coil defines an excitation node.

A signal processing circuit for an inductive position sensor having at least an excitation coil, an output coil, and a core disposed adjacent and movable relative to the excitation coil and the output coil, the signal processing circuit comprising:

• a plurality of resistors, each of the resistors having a first terminal and a second terminal and a resistance value unequal to another one of the resistors, the first terminal of each resistor adapted to receive a voltage from an electric power source;
• and
• a processor having a plurality of pins, each of the pins individually coupled to the second terminal of one of the resistors, the processor configured to:
• selectively draw current from the electric power source through each of the resistors to thereby generate and supply a stair-step sinusoidal excitation voltage for the excitation coil, and
• receive an output signal from the output coil, and
• upon receipt of the output signal, supply a position signal representative of relative core position.