| 摘要 |
<p>A pneumatically operated cascade control system comprising a primary controller producing an output signal as the set point for a cascaded secondary controller which controls the setting of a process valve. The secondary controller incorporates planar pneumatic technology wherein a thin sheet or plate of metal is formed with openings to define pressure-receptive segments which are pivotable about pivot axes at selected regions. This plate forms part of a laminar sandwich having wall means which cooperate with the plate segments to define pressure chambers to some of which various pressure signals are directed to cause the plate segments to pivot about their pivot axes. Output pressure signals are derived from other of the pressure chambers. The cascade control system comprises transfer switching means for transferring between automatic and manual modes in a bumpless, balanceless fashion. All of the controls required by the process operator are available at the front panel of the instrument, while additional controls for the specialized purposes of maintenance personnel are located in the interior of the instrument with restricted availability.</p> |
