| 摘要 |
PURPOSE:To improve fault judging accuracy, by calculating propagation delay time of sampling signal between respective devices and outputting a sampling signal at a time where the propagation delay time is considered, thereby obtaining sampling data at same time in respective devices. CONSTITUTION:A central relay device 1 for producing a reference sampling signal and a plurality of terminals 8 for collecting signals are coupled in loop through cables 9, 10 so as to transmit a sampling signal to lower-order devices sequentially from upper-order devices. Synchronous arithmetic circuits 4 are provided to respective devices 1, 8. A transmitting/receiving section for returning the sampling signal to the upper-device and a timer section are provided in the synchronous arithmetic circuit 4 in order to measure a time TX to be elapsed until a signal transmitted to a lower device is returned. Then (TP - TX/2) is calculated for a time interval TP between transmission and reception of sampling signal, and upon elapse of the calculated time, sampling signal is transmitted again to the lower-order device. |
