A new method for the measurement of low speed using a multiple-electrode capacitive sensor

A novel method for the measurement of low speeds by using a low-cost capacitive sensor is presented. Its main advantages are its simplicity, low cost and the very low speed (as low as 0.02 rad/s), which can be measured with a relatively high resolution in a short measurement time. The multiple capacitors, whose values are piece-wise linearly related to the position in a periodic way, are used as the sensing elements of the low-speed sensor. A capacitance-controlled oscillator is used in the processing circuit to convert the capacitance to a period-modulated signal which can be read directly out by a microcontroller. An algorithm, which is used to calculate the speed from the measured periods, either eliminates or strongly reduces the influence of most errors. The measurement time is relatively short for low speeds. Meanwhile, the direction of movement can be indicated