| 摘要 |
PURPOSE:To prevent the abnormality of a system by performing selection of the set value from a computer and the set value from an operator station in two stages first up to a controller then up to a control object. CONSTITUTION:The set values from a computer 1 and an operator station 2 are selected by the contacts 9, 10 of the 1st relay 7. A controller 3 compares the set values and the feedback signal from the object 5, and outputs command values to an electric motor value positioner 4. Here, when the 1st relay 7 is disabled, contacts 20, 22 make first, and contacts 19, 21 break. At the same time, contacts 13 break as well, and the self-latching of the 2nd relay 6 is released and therefore contacts 15, 17 break and the output of the electric motor valve positioner is disconnected. When a new set value is applied from the station 2, and the 3rd relay 3 is operated in putting the set pulses thereto, the 3rd relay 8 is latched by contacts 12 because it has approximately the same constitution as that of the 2nd relay 6. At the same time, contacts 16, 18 make and since the contacts 20, 22 of the 1st relay 7 make, the output of the positioner 4 is connected to the object 5. |
