Abstract: A method for detecting a change in permeability of a magnetostrictive object due to a change in strain. At least one first coil and at least one second coil are obtained and positioned such that magnetic flux lines induced by an electric current in the first coil(s) pass through at least one portion of the object in a direction substantially parallel to the strain direction, such that magnetic flux lines induced by an electric current in the second coil(s) pass through at least one portion of the object in a direction substantially parallel to the strain direction, and such that any electromagnetic interference sensed by the first coil(s) is sensed oppositely by the second coil(s). The total inductance of the positioned first and second coil(s) is measured over time. A change in permeability of the object is detected from a change in the measured total inductance over time.

Abstract: A resistor (having a resistance of Rs) is connected in series with an inductor whose inductance and/or resistance is desired to be determined. An alternating voltage (such as a sinusoidal voltage) is applied across the series-connected resistor and inductor, wherein the alternating voltage has a frequency ?, a unique maximum or minimum value Vm, an average value and a unique crossover of the average value. The voltage Vr is measured across the resistor when the alternating voltage is at its maximum or minimum value. The voltage Vl is measured across the resistor when the alternating voltage is at its average value. The resistance RL of the inductor is calculated from an equation in which RL is a function of Vm, Vr , Rs and Vl. The inductance L of the inductor is calculated from an equation in which L is a function of Vl, Rl, Rs, Vr and ?.

Abstract: A method and circuit for detecting a change in inductance of a variable inductance element. An oscillating signal has a frequency that varies with inductance of the element. An intermediate voltage is produced at a level that varies according to frequency of the oscillating signal. The intermediate voltage is scaled to produce an output voltage.

Abstract: A resistor (having a resistance of Rs) is connected in series with an inductor whose inductance and/or resistance is desired to be determined. An alternating voltage (such as a sinusoidal voltage) is applied across the series-connected resistor and inductor, wherein the alternating voltage has a frequency ?, a unique maximum or minimum value Vm, an average value and a unique crossover of the average value. The voltage Vr is measured across the resistor when the alternating voltage is at its maximum or minimum value. The voltage Vl is measured across the resistor when the alternating voltage is at its average value. The resistance RL of the inductor is calculated from an equation in which RL is a function of Vm, Vr, Rs and Vl. The inductance L of the inductor is calculated from an equation in which L is a function of Vl, Rl, Rs, Vr and ?.

Abstract: A method for detecting a change in permeability of a magnetostrictive object due to a change in strain. At least one first coil and at least one second coil are obtained and positioned such that magnetic flux lines induced by an electric current in the first coil(s) pass through at least one portion of the object in a direction substantially parallel to the strain direction, such that magnetic flux lines induced by an electric current in the second coil(s) pass through at least one portion of the object in a direction substantially parallel to the strain direction, and such that any electromagnetic interference sensed by the first coil(s) is sensed oppositely by the second coil(s). The total inductance of the positioned first and second coil(s) is measured over time. A change in permeability of the object is detected from a change in the measured total inductance over time.

Abstract: A resistor (having a resistance of Rs) is connected in series with an inductor whose inductance and/or resistance is desired to be determined. An alternating voltage (such as a sinusoidal voltage) is applied across the series-connected resistor and inductor, wherein the alternating voltage has a frequency &ohgr;, a unique maximum or minimum value Vm, an average value and a unique crossover of the average value. The voltage Vr is measured across the resistor when the alternating voltage is at its maximum or minimum value. The voltage Vl is measured across the resistor when the alternating voltage is at its average value. The resistance RL of the inductor is calculated from an equation in which RL is a function of Vm, Vr, Rs and Vl. The inductance L of the inductor is calculated from an equation in which L is a function of Vl, Rl, Rs, Vr and &ohgr;.