| 摘要 |
PURPOSE:To detects open circuits of signal lines for the phases A and B of a rectangular wave and to prevent malfunction due to a noise by combining the analog sine wave signal of an encoder capable of detecting an open circuit with the rectangular wave signals of the phases A and B multiplied by this signal. CONSTITUTION:If at least one of the lines for the phases A and B is discontinued at least one of inputs of a device which performs OR operation goes up to a level High since the inputs are pulled up to the source voltage of an open circuit detector by a proper resistor and the output of the device 2 which performs the OR operation is fixed at the level High, so that a counter 4 can not be reset. The counter 4 counts up with the output of a waveform shaping device 3 and when a constant value is reached, the counter 4 inputs an open circuit detection signal to a holding device 5 for an open circuit signal, thereby detecting the disconnection of the phase A or B. If an analog sine wave signal is cut off, the signal is not inputted to the counter 4 and the open circuits of the A-phase and B-phase signals can not be detected. In this case, they are detected by an open circuit detector 6. |
