Low-cost, accurate capacitive encoders
Misgav, Israel -An innovative, noncontact encoder design based on variable capacitance sensing promises to bring industrial-quality performance (up to 18-bit angular resolution or 10stationary field transmitter, field receiver, processing circuitry, and a dielectric rotor that interacts electrically with the receiver to produce 'pure' sine and cosine dc output signals proportional to the rotation angle. (Rotor and transmitter contain conductive patterns on their surfaces.) Since outputs are dc sig-nals rather than pulses, no ac excitation or demodulation is involved. A combination of coarse/fine output determines absolute posi-tion over 360°. Reportedly, submicron resolution can be derived from the signals. Electric Encoder's benefits include low power consumption,magnetic/RFI immu-nity, and tolerance to industrial conditions due to its 'holistic' rotor design that makes large areas of the rotor active in the sensing at a given time.