Operation of inductive distance sensor by scaling output signal by vectorially obtained factor

Claim 1

A method of operating an inductive distance sensor for measurement of a load, the sensor comprising a vane, a first coil and a second coil which is connected electrically in series with the first coil and is spaced apart from the first coil, said vane being movable between said first and said second coils to change its relative distance from the coils and thus the magnitudes of their inductances L 1 and L 2 , a position of said vane between the coils being under the influence of a measurement variable, the method comprising the steps of: applying a first sinusoidal voltage U e1 to said first coil and a second sinusoidal voltage U e2 to said second coil, said sinusoidal voltages being of equal amplitude and opposite phase; tapping off from a terminal connected between the coils an output signal having a voltage U S with respect to zero potential; determining U eR and U eL of (U e =U e1 +U e2 ) with respect to magnitude and phase; measuring a vectorial part U sL of U S which is in phase with U eL ; and multiplying the value of U sL by a ratio U e /U eL for obtaining a measurement of the load.

Claim 2

A method of operating an inductive distance sensor for measurement of a load, the sensor comprising a vane, a first coil and a second coil which is connected electrically in series with the first coil and is spaced apart from the first coil, said vane being movable between said first and said second coils to change its relative distance from the coils and thus the magnitudes of their inductances L 1 and L 2 , a position of said vane between the coils being under the influence of a measurement variable, the method comprising the steps of: applying a first sinusoidal voltage U e1 to said first coil and a second sinusoidal voltage U e2 to said second coil, said sinusoidal voltages being of equal amplitude and opposite phase; tapping off from a terminal connected between the coils an output signal having a voltage U S with respect to zero potential; determining U eR and U eL of (U e =U e1 +U e2 ) with respect to magnitude and phase; measuring a vectorial part U sL of U S which is in phase with U eL ; and multiplying the value of U sL by a ratio U e /U eL for obtaining a measurement of the load.

Claim 3

A method of operating an inductive distance sensor for measurement of a load, the sensor comprising a vane, a first coil and a second coil which is connected electrically in series with the first coil and is spaced apart from the first coil, said vane being movable between said first and said second coils to change its relative distance from the coils and thus the magnitudes of their inductances L 1 and L 2 , a position of said vane between the coils being under the influence of a measurement variable, the method comprising the steps of: applying a first sinusoidal voltage U e1 to said first coil and a second sinusoidal voltage U e2 to said second coil, said sinusoidal voltages being of equal amplitude and opposite phase; tapping off from a terminal connected between the coils an output signal having a voltage U S with respect to zero potential; employing a reference sensor consisting of an ohmic precision resistance divider, and applying thereto the sinusoidal voltages U e1 +U e2 =U e of which there is a middle-point voltage U M with respect to zero potential; measuring the middle point voltage U M ; establishing a voltage portion U MR which is identical in polarity to U e1 and of the same phase as U e ; establishing a voltage portion U ML of U M which is shifted in phase by 90° to U MR , wherein U MR is the real part of U M , and U ML is the imaginary part of U M ; storing values of the voltages U MR and U ML ; applying a voltage U e equal to the sum of U e1 and U e2 to the inductive distance sensor and determining the voltages U e , U eR and U eL as well as the corresponding phase angle α of U e ; measuring the voltage portion U sL of U s which is in the same phase as U eL ; and correcting U sL by subtraction of ΔU sL which equals U MR ×sin α+U ML ×cos α to obtain a measurement of the load.

Claim 4

A method of operating an inductive distance sensor for measurement of a load, the sensor comprising a vane, a first coil and a second coil which is connected electrically in series with the first coil and is spaced apart from the first coil, said vane being movable between said first and said second coils to change its relative distance from the coils and thus the magnitudes of their inductances L 1 and L 2 , a position of said vane between the coils being under the influence of a measurement variable, the method comprising the steps of: applying a first sinusoidal voltage U e1 to said first coil and a second sinusoidal voltage U e2 to said second coil, said sinusoidal voltages being of equal amplitude and opposite phase; tapping off from a terminal connected between the coils an output signal having a voltage U S with respect to zero potential; employing a reference sensor consisting of an ohmic precision resistance divider, and applying thereto the sinusoidal voltages U e1 +U e2 =U e of which there is a middle-point voltage U M with respect to zero potential; measuring the middle point voltage U M ; establishing a voltage portion U MR which is identical in polarity to U e1 and of the same phase as U e ; establishing a voltage portion U ML of U M which is shifted in phase by 90° to U MR , wherein U MR is the real part of U M , and U ML is the imaginary part of U M ; storing values of the voltages U MR and U ML ; applying a voltage U e equal to the sum of U e1 and U e2 to the inductive distance sensor and determining the voltages U e , U eR and U eL as well as the corresponding phase angle α of U e ; measuring the voltage portion U sL of U s which is in the same phase as U eL ; and correcting U sL by subtraction of ΔU sL which equals U MR ×sin α+U ML ×cos α to obtain a measurement of the load.