A liquid-level control system can be configured in either of two ways. with a control valve manipulating flow of liquid into the holding tank (Figure a), or with a control valve manipulating the flow of liquid from the tank (Figure b). Assuming that the liquid- level transmitter always is direct acting,
(a) For each configuration, what control action should a proportional pneumatic controller have if the control valve is air-to-open?
(b) If the control valve isair-to-close?

pur-new-sol