P1.2 Control systems can use a human operator as part of a closed-loop control system. Sketch the block diagram of the valve control system shown in Figure P1.2.P1.3 In a chemical process control system, it is valuable to control the chemical composition of the product.

To do so, a measurement of the composition can be obtained by using an infrared stream analyzer, as shown in Figure P1.3. The valve on the additive stream may be controlled. Complete the control feedback loop, and sketch a block diagram describing the operation of the control loop.

Human operator Fluid flow Output Meter Process Valve FIGURE P1.2 Fluid-flow control.