| 摘要 |
1521815 Automatic control YOKOGAWA ELECTRIC WORKS Ltd 4 June 1976 [17 June 1975] 23145/76 Heading G3N A process control system, complying a digital data processing arrangement, incorporates facilities for servicing. As shown, field sensing devices 1, such as thermocouples generate analog signals which, together with contact signals 1', are fed over a line 3 to a signal converter 4. The converter 4 comprises units ACB deriving PWM signals from the analog signals which are manipulated to derive analog control signals for valves 2. Each unit ACB is isolated through a transformer or photo-coupler. The outputs/inputs of units ACB are fed to a digital control device 9 or an editor 6, which is set up to route signals between converter 4 and the device 9 or an analog processing device 10 via a converter unit 12. An alarm device and a trend recorder are incorporated in unit 12. On-off contact signals l'are routed through a digital input board DIB to a memory DGN and used to control on-off valves 2' through a relay board ROB. The device 9 comprises a micro-computer SCU and device 11 a manual/automatic unit MBU/ABU and a maintenance back-up unit PMU operating as a stand-by for the signal converter device 4. |
