Problem 1 Consider two possible ways to control a desired rate of liquid flow us
ID: 637797 • Letter: P
Question
Problem 1 Consider two possible ways to control a desired rate of liquid flow using proportional feedback control. Both Systems (a) and (b), the flow transmitter Km is direct acting. The control valve in System (a) "air-to open." Meaning that an increasing pressure signal from the controller will open the valve more, thus increasing the flow rate. On the other hand, the control valve in System (b) is "air-to-close." FC FC FT IT Liquid (a) For each of these valves. what is the sign of its gain, Kv? (b) Which controller must be direct acting? Reverse acting? (c) What sign should the controller gain have for each case? (d) what should be the overall sign (Kc"KV"km)?Explanation / Answer
a) kv is positive for (a) & negative for (b)
B) controller (a) is reverse acting controller (b) is direct acting
C) controller gain is Positive for (a) & negative for (b)
D) overall sign is always positive