Device and method for determining frequency and amplitude of an oscillating structure, especially for measuring acceleration or rotational rates
First Claim
1. Apparatus for determining frequency and/or amplitude of a vibrating structure adapted for the measurement of acceleration and angular velocity comprising:
- a fixed element, a movable element facing said fixed element at a distance therefrom, said movable element being excited in periodic vibration about an axis of vibration in a plane of the movable element for undergoing angular vibrating movement around said axis of vibration towards and away from said fixed element, first and second position sensors spaced at different distances from said axis of vibration for measuring distance of said movable element from said fixed element as said movable element undergoes vibration around said axis, the first and second sensors respectively including sensor elements supported at different levels on said movable element so that as the movable element vibrates the sensor elements of the first and second sensors are at equal distances from the fixed element for one particular angular position of the movable element in each half wave of the vibration thereof and are at different distances from the fixed element at all other angular positions of the movable element during said vibration thereof, a comparator for comparing distance measurements of the sensor elements to determine a threshold value at which the distance measurements are equal and the movable element is at said one angular position in each half wave of vibration, and a device for determining amplitude and/or frequency of vibration of the movable element from said threshold value, independently of the distance of the movable element from the fixed element.
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Accused Products
Abstract
A device for determining the frequency and/or the amplitude of a vibrating structure includes a vibrating element (2) and a pair of position sensors (10, 11) for the determination of the deflection of the vibrating element (2). The position sensors (10, 11) are arranged such that their measurements during a half-wave of vibration exceed and/or are less than one another. A comparator compares the measurements of the two position sensors (10, 11) to determine a threshold value Us for the half-wave of the vibration at which their measurements are equal. A device is used for determining the duration during which the measurement of one of the two position sensors (10, 11) exceeds or is less than the threshold value Us. The position sensors (10, 11) can be capacitors whose electrodes are arranged in a step-like manner. The determination of the amplitude of the vibration is, carried out independent of a potential parallel shift of the movable element (2), such that there is no distortion of the measurement result.
21 Citations
17 Claims
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1. Apparatus for determining frequency and/or amplitude of a vibrating structure adapted for the measurement of acceleration and angular velocity comprising:
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a fixed element, a movable element facing said fixed element at a distance therefrom, said movable element being excited in periodic vibration about an axis of vibration in a plane of the movable element for undergoing angular vibrating movement around said axis of vibration towards and away from said fixed element, first and second position sensors spaced at different distances from said axis of vibration for measuring distance of said movable element from said fixed element as said movable element undergoes vibration around said axis, the first and second sensors respectively including sensor elements supported at different levels on said movable element so that as the movable element vibrates the sensor elements of the first and second sensors are at equal distances from the fixed element for one particular angular position of the movable element in each half wave of the vibration thereof and are at different distances from the fixed element at all other angular positions of the movable element during said vibration thereof, a comparator for comparing distance measurements of the sensor elements to determine a threshold value at which the distance measurements are equal and the movable element is at said one angular position in each half wave of vibration, and a device for determining amplitude and/or frequency of vibration of the movable element from said threshold value, independently of the distance of the movable element from the fixed element. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
wherein Us is amplitude of the threshold value, Tp is a time interval between successive threshold values in a half-wave of vibration and fs is the frequency of vibration.
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11. The apparatus of claim 1, wherein said fixed element and said movable element are in the form of plates.
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12. A method for determining frequency and/or amplitude of a vibrating structure adapted for measurement of acceleration and angular velocity comprising the steps of:
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vibrating a plate element in periodic vibration about an axis in a plane of the plate towards and away from a fixed datum, supporting two position sensors on the plate element for measuring distance of the vibrating plate with respect to the fixed datum, arranging the position sensors on the plate to obtain a threshold value (Us) during a half-wave of vibration of the plate at which the distances measured by the two position sensors from the fixed datum are equal, determining time duration (Tp) in the half-wave of the vibration between successive threshold values, and determining frequency or amplitude or both of vibration of the plate from the threshold value Us and time duration Tp independently of spacing between the movable plate and the fixed datum. - View Dependent Claims (13, 14, 15, 16, 17)
wherein Us is amplitude of the threshold value, Tp is the time interval between successive threshold values in a half-wave of vibration and fs is the frequency of vibration.
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17. The method of claim 12, wherein the threshold value (Us) is obtained by supporting the position sensors at different elevations on the vibrating plate.
Specification