| 摘要 |
Disclosed is a variable capacitance type encoder for measuring the length of an object to be measured on the basis of the amount of a probe which is brought into contact with the object. The amount of the movement of the probe is detected by the variation of electrostatic capacity between a rotary disc which is secured to the shaft, e.g., threaded shaft of the probe, and fixed plates which are secured to a baseplate so as to be opposed to the rotary disc. Two fixed plates are opposed to the rotary disc, and at least one fixed plate is provided with first and second transmitting electrodes composed of a pluarlity of electrode elements to which voltages of different phases are applied and which are annularly arranged at regular intervals in the circumferential direction of the fixed plate. The phase difference between the voltages which are applied to both transmitting electrodes is 180 DEG . On the other hand, the rotary disc is provided with first and second receiving electrodes for receiving signals of a common phase by electrostatic coupling with both transmitting electrodes. Each fixed plate is provided with an output electrode which electrostatically couples with the respective receiving electrode for fetching a signal through electrostatic coupling.
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