Eddy current proximeter
AssigneeTransducer Limited Partnership
InventorWilliam W. Carr
Life of this patent
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Abstract
An inductive sine wave oscillator circuit for an eddy current proximeter. The oscillator circuit includes an operational amplifier and a coil. The frequency and amplitude of the output signal produced by the circuit varies with and is controlled by the inductance of the coil. The circuit signal input to the operational amplifier undergoes a phase shift as the signal passes through the amplifier. One advantage of the oscillator circuit is that the frequency and amplitude of the output signal of the circuit for a coil having a particular inductance remains relatively stable and constant when the operating temperature of the coil varies. In addition, the coil can be fabricated from a material having a relatively high electrical resistivity.
Claims2
An inductive oscillator circuit including
- a. a amplifier having a phase shift and an output and an input, said input including a positive input terminal and a negative input terminal;
- b. first positive feedback means connecting said amplifier output to said amplifier positive input terminal;
- c. second negative feedback means connecting said amplifier output to said amplifier negative input terminal;
- d. inductive means including first resistor means;
- e. means connecting said inductive means to said first feedback means to produce a signal at said positive input terminal which is variable in accordance with the inductance of said inductive means, said inductive means causing a phase shift in said voltage signal traveling through said first feedback means from said output to said positive input terminal;
- f. second resistor means in said first positive feedback means;
- and
- g. third resistor means in said second negative feedback means;
- said phase shift of said amplifier enabling
- h. said phase shift in said voltage signal traveling through said first feedback means;
- and,
- i. oscillation to occur in said circuit.
Dependencies are inferred from the claim text.