OSCILLATION SENSOR WITH CALIBRATION UNIT AND MEASUREMENT DEVICE
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Abstract
The invention relates to an oscillating sensor for a measurement device comprising:
- an oscillator comprising:
- a resonance circuit for providing an oscillation signal;
- a gain stage configured to provide a feed-back to the resonance circuit to inject energy for excitation of the oscillator to maintain oscillation;
- at least one calibration element to adjust the open loop gain of the oscillator;
- a calibration unit to provide a modulated calibration control signal to selectively adjust an electrical measure of the at least one calibration element based on at least one predetermined duty cycle,
- wherein the calibration unit is further configured to provide the modulated calibration control signal with at least one cycle frequency which depends on the oscillation frequency.
- an oscillator comprising:
5 Citations
26 Claims
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1-12. -12. (canceled)
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13. Oscillating sensor for a measurement device comprising:
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an oscillator comprising; a resonance circuit for providing an oscillation signal; a gain stage configured to provide a feed-back to the resonance circuit to inject energy for excitation of the oscillator to maintain oscillation; at least one calibration element to adjust the open loop gain of the oscillator; a calibration unit to provide a modulated calibration control signal to selectively adjust an electrical measure of the at least one calibration element based on at least one predetermined duty cycle, characterized in that the calibration unit is further configured to provide the modulated calibration control signal with at least one cycle frequency which depends on the oscillation frequency.
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14. Oscillating sensor according to claim 13, wherein the modulated calibration control signal corresponds to a pulse width modulation signal.
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15. Oscillating sensor according to claim 13, wherein the calibration element is configured to be controlled by a modulated calibration feedback control signal wherein particularly the calibration element includes a passive electrical component, particularly a resistor, and a switch controlled by a modulated calibration feedback control signal.
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16. Oscillating sensor according to claim 13, wherein the calibration element includes a gain control element to be controlled by a modulated calibration gain control signal for adjusting the gain of the gain stage wherein particularly the calibration element includes a resistor and a switch controlled by the modulated calibration gain control signal.
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17. Oscillating sensor according to claim 13, wherein the calibration unit is configured to maintain the at least one duty cycle while varying the cycle frequency.
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18. Oscillating sensor according to claim 13, wherein the calibration unit is configured to set the cycle time or cycle frequency to a value where the amplitude modulation of the oscillation signal is lower than 1%, preferably lower than 0.1% of the total oscillation amplitude.
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19. Oscillating sensor according to claim 17, wherein the calibration unit is configured to set the cycle time or cycle frequency to a value where the amplitude modulation of the oscillation signal is lower than 1%, preferably lower than 0.1% of the total oscillation amplitude.
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20. Oscillating sensor according to claim 13, wherein the calibration unit is configured to set the cycle frequency to a value which is selected from one of frequency ranges which are determined by cycle times which are selected from a range where the cycle time is distanced from the (n 1/2) times the oscillation cycle time cycle time by more than 2% and not more than 25%, preferably by more than 5% not more than 15% of the oscillation cycle time., wherein the oscillation cycle time corresponds to the oscillating frequency.
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21. Oscillating sensor according to claim 18, wherein the calibration unit is configured to set the cycle frequency to a value which is selected from one of frequency ranges which are determined by cycle times which are selected from a range where the cycle time is distanced from the (n 1/2) times the oscillation cycle time cycle time by more than 2% and not more than 25%, preferably by more than 5% not more than 15% of the oscillation cycle time., wherein the oscillation cycle time corresponds to the oscillating frequency.
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22. Oscillating sensor according to claim 19, wherein the calibration unit is configured to set the cycle frequency to a value which is selected from one of frequency ranges which are determined by cycle times which are selected from a range where the cycle time is distanced from the (n 1/2) times the oscillation cycle time cycle time by more than 2% and not more than 25%, preferably by more than 5% not more than 15% of the oscillation cycle time., wherein the oscillation cycle time corresponds to the oscillating frequency.
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23. Oscillating sensor according to claim 13, wherein a frequency counter is provided to measure the oscillation frequency of the oscillator and to provide an indication of the oscillation frequency to the calibration unit.
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24. Oscillating sensor according to claim 13, wherein the resonance circuit has a sensing coil and/or a sensing capacitor.
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25. Measurement device comprising an oscillating sensor and an analyzing circuit which is configured to receive an indication of the oscillation signal and to provide an amplitude signal as a sensor signal indicating the amplitude of the oscillation signal.
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26. Measurement device according to claim 25, wherein the resonance circuit has a sensing coil for detecting a conductive object being in a sensing range of the sensing coil.
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26-1. Method for operating an oscillation sensor comprising a resonance circuit for providing an oscillation signal, a gain stage configured to feed back to the resonance circuit to inject energy for excitation of the resonance circuit to maintain oscillation, and at least one calibration element to adjust the feedback coupling between the gain stage and the resonance circuit, wherein an electrical measure of the at least one calibration element is adjusted based on at least one predetermined duty cycle of a modulated calibration control signal
characterized in that the modulated calibration control signal has at least one cycle frequency, which depends on the oscillation frequency.
Specification