| 摘要 |
1,188,847. Electric correspondence control systems. HONEYWELL Ltd. Sept. 5, 1968 [Sept. 8, 1967], No.41128/67. Heading G1N. [Also in Division G3] In a process control system comprising two or more control stations 1, 2 each having a manually adjustable potentiometer 3, 3a for generating a set point signal and means 11, 11a for indicating the value of the set point signal, manual adjustment of the set point potentiometer at any one of the stations causes a corresponding adjustment to be made at each other station to maintain the values of the set point signals generated at all the stations equal. As shown in Fig. 1, each station has a servomotor 19, 19a which is normally used to drive an indicator 25, 25a for indicating the value of the process variable being controlled, but when, for example, a wheel 12a at station 2 is depressed ready to adjust potentiometer 3a, a switch 27a is closed thereby energizing a coil 29 in station 1 to change a switch 17 from the position shown in full lines to the position shown in dotted lines and also energizing a further coil 31 in station 1 to operate a clutch to lock together the wheels 4 and 21 so that when the wheel 12a is turned to adjust potentiometer 3a, servomotor 19 operates to adjust potentiometer 3. A controller 33 receives the process variable signal from terminal 14 and the set point signal via switch 36 from one of the control stations and delivers an amplified error signal which is used for controlling the process variable concerned. Each control station may also include a further servosystem, Fig. 2 (not shown), for indicating the value of the control signal and a switch (66, 66a) enabling a bumpless change to manual control using the balancing potentiometer (60, 60a) of the further servosystem as a transmitter. During manual control, a feedback circuit keeps the output of controller 33 equal to the control signal generated by the manual control so that change back to automatic control is bumpless. Interlocks and warning lights are provided to prevent manual operation from two stations simultaneously. Plug-in connections may be provided between the control stations and a junction box 48. Several controllers 33 may be provided, each connected through a respective junction box 48 to a single control station, and a second control station may be plugged in at will to any one of the junction boxes 48. |
