A process control system

875,079. Automatic control-systems. ZAVODY PRUMYSLOVE AUTOMATISACE NARODNI PODNIK PRAHA. June 6, 1958, No. 18157/58. Class 38 (4). As shown, a proportional controller 2, responsive to a variable quantity associated with a plant 1, controls plant 1 to maintain the quantity at a predetermined value automatically. Two additional control signals are introduced into a summator 4, one, aiding, being derived directly from a second, higher adjustable gain, proportional controller 3, and the other, opposing, being derived from controller 3 through an adjustable delay unit 5. The arrangement is such that the two additional signals cancel out after the delay period. The control signals may be hydraulic, pneumatic or electric. In the latter case the delay unit may be a resistancecapacity circuit and the summator a bridge circuit.