Instrument for measuring lengths or angles
First Claim
1. A linear or angular measuring instrument comprising a capacitance sensor having a linear or curvilinear array of sensor electrodes, a scale facing said sensor and having an array of scale features, switching means for a) connecting first selected ones of the sensor electrodes to first means providing them with electrical signals so that they become part of a first spatially periodic pattern of momentarily transmitting electrodes and b) connecting second selected ones of the sensor electrodes to second means so that they become part of a second spatially periodic pattern of momentarily receiving electrodes, said second means determining a relative position of the sensor along the scale, wherein attribution of a sensor electrode to one of said first or second spatially periodic patterns is controlled by control means adapted to shift said first and said second spatially periodic patterns alternately by increments along said array of sensor electrodes so that the shifts of one spatially periodic pattern take place during the intervals between the shifts of the other spatially periodic pattern, the shifts of the first spatially periodic pattern being thus picked up by said second spatially periodic pattern of momentarily receiving electrodes, such that an electrode can be caused to become both transmitting and receiving during the course of a measurement said first and said second spatially periodic patterns being interleaved along said linear or curvilinear array of juxtaposed momentarily transmitting and receiving electrodes.
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Abstract
The capacitance sensor (1) comprises a linear or curvilinear array of electrodes (10) connected to means generating on these electrodes (10) a spatially periodic electric potential pattern shifting by increments along said array. Electrodes (10) are disconnected in turn to act as momentarily receiving electrodes (10R), also according to a spatially periodic pattern, shifting by the same increments. Both patterns shift alternately, i.e. the shifts of one pattern taking place between the shifts of the other. A linear or curvilinear scale (2), with a periodic pattern of electrodes (20) or dielectric or conducting relief, facing the sensor, will thus create a periodic fluctuation of the signal coupled on the momentarily receiving electrodes. The relative position between scale (2) and sensor (1) may then be accurately determined by evaluating the phase, after demodulation, of said signal. As the sensor may be integrated on a semiconductor die and the scale may be very narrow, extreme miniaturization and low cost is given. (FIGS. 1a and 1b)
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Citations
16 Claims
- 1. A linear or angular measuring instrument comprising a capacitance sensor having a linear or curvilinear array of sensor electrodes, a scale facing said sensor and having an array of scale features, switching means for a) connecting first selected ones of the sensor electrodes to first means providing them with electrical signals so that they become part of a first spatially periodic pattern of momentarily transmitting electrodes and b) connecting second selected ones of the sensor electrodes to second means so that they become part of a second spatially periodic pattern of momentarily receiving electrodes, said second means determining a relative position of the sensor along the scale, wherein attribution of a sensor electrode to one of said first or second spatially periodic patterns is controlled by control means adapted to shift said first and said second spatially periodic patterns alternately by increments along said array of sensor electrodes so that the shifts of one spatially periodic pattern take place during the intervals between the shifts of the other spatially periodic pattern, the shifts of the first spatially periodic pattern being thus picked up by said second spatially periodic pattern of momentarily receiving electrodes, such that an electrode can be caused to become both transmitting and receiving during the course of a measurement said first and said second spatially periodic patterns being interleaved along said linear or curvilinear array of juxtaposed momentarily transmitting and receiving electrodes.
Specification