Sensor apparatus and method for generating signals indicative of the position or change in position of limbs
A sensor apparatus for generating electrical signals which indicate the position or movement of limbs relative to a reference area has a transmitter electrode apparatus, a voltage generator for applying an alternating voltage to the transmitter electrode, a first receiver electrode apparatus, a second receiver electrode apparatus, and a third receiver electrode apparatus, wherein the first, second, and third receiver electrode apparatuses are each connected to high-impedance tapping systems. The first, second, and third receiver electrode apparatuses are preferably each connected to high-impedance inputs of an impedance transformer system, wherein information indicative of a location or movement is obtained on the basis of differences between the electrical events present at the outputs of the respective impedance transformer.
1. A sensor apparatus for determining a spatial position or movement of limbs, the apparatus comprising:
a transmitter electrode,
a voltage generator for applying an alternating voltage to the transmitter electrode,
a first receiver electrode,
a second receiver electrode, and
a third receiver electrode, and
first, second, and third impedance transformers each having a high impedance input each receiving a voltage from the first, second, and third receiver electrode, respectively,
a mean value circuit coupled with the outputs of the first, second, and third impedance transformers;
a first differential amplifiers for generating a differential value between the output of the first impedance transformer and the output of the mean value circuit;
a second differential amplifiers for generating a differential value between the output of the second impedance transformer and the output of the mean value circuit;
a third differential amplifiers for generating a differential value between the output of the third impedance transformer and the output of the mean value circuit.
2. The sensor apparatus according to claim 1 wherein information indicative of a location or movement is obtained on the basis of differences between electrical signals present at the outputs of the respective impedance transformer.
3. The sensor apparatus according to claim 2 wherein a divider divides the composite signal to generate the mean value.
4. The sensor apparatus according to claim 2 comprising synchronous detectors, which generate signals indicative of the synchronicity of the output signal at the respective impedance transformers with the alternating voltage.
5. The sensor apparatus according to claim 4 wherein the information indicative of a location or movement is obtained on the basis of differences between the electrical signals present at the outputs of the respective synchronous detector.
6. The sensor apparatus according to claim 4 wherein each synchronous detector provides signals indicative of the synchronicity of a voltage level compared to the alternating voltage.
7. The sensor apparatus according to claim 4 wherein the synchronous detector provides signals indicative of the synchronicity of a phase compared to the alternating voltage.
8. The sensor apparatus according to claim 4 further comprising an ADC receiving output signals of the synchronous detector, wherein the ADC is coupled a microcontroller unit for evaluation.
9. The sensor apparatus according to claim 1 further comprising an amplifier for amplifying the output of the mean value circuit.
10. The sensor apparatus according to claim 1 wherein the receiver electrodes are disposed symmetrically around the transmitter electrode.
11. The sensor apparatus according to claim 1 wherein the transmitter electrode is supplied by a generator with an alternating current and produces a surrounding electrical field.
12. The sensor apparatus according to claim 1 wherein the receiver electrodes are disposed symmetrically around the transmitter electrode.
13. The sensor apparatus according to claim 1 wherein the voltages present at the receiver electrodes contains information about the distribution of the field of the transmitter electrode.
14. The sensor apparatus according to claim 1 wherein the voltages present at the receiver electrodes are present at the receiver electrodes of channels 1 , 2 , and 3 .
15. The sensor apparatus according to claim 1 wherein each differential amplifier is coupled with a diode rectifier.
16. The sensor apparatus according to claim 1 wherein each differential amplifier is coupled with a peak detector.
17. The sensor apparatus according to claim 1 further comprising an ADC directly coupled with the outputs of the first, second, third differential amplifier.
18. A method for generating electrical signals that indicate the position or movement of limbs, the method comprising the steps of
applying an alternating electrical field to a transmitter electrode, and receiving voltages by at least three receiver electrodes disposed in the vicinity of the transmitter electrode,
feeding the received voltages to high impedance inputs of impedance transformers;
forming a mean value of output signals from the impedance transformers;
forming first, second and third differential signals between the mean value and the output values of the respective impedance transformers.
19. The method according to claim 18 , further comprising amplifying the mean value.
20. The method according to claim 19 , further comprising feeding the amplified mean value to an ADC.
21. The method according to claim 19 , further comprising feeding the differential signals and the amplified mean value to an ADC and determining the position or a movement of a limb from said differential signals and said amplified mean value.
22. The method according to claim 18 , further comprising determining synchronicity of the differential signals with the alternating electrical field.
23. The method according to claim 22 , further comprising feeding the synchronous detection signals to an ADC.
24. The method according to claim 18 , further comprising feeding the differential signals to an ADC.