Process Control Systems Liquid Level Control LAP 7 ON/OFF control: An on-off controller is the simplest form to control an operation. The output from the device is either on or off, with no middle state. An on-off controller will switch the output only when for example the temperature crosses the set point. Deadband (sometimes called a neutral zone or dead zone) is an interval of a signal domain or band where no action occurs. Narrow deadband causes high oscillation, therefore reduces the lifetime of component. Wide deadband reduces oscillation, but has higher error. Electromechanical relay ON/OFF control Program a Honeywell UDI 1700 Process meter’s discrete outputs to control alarms. Use a Honeywell UDI 1700 Process meter to perform ON/OFF control. Closed loop systems: Systems that utilize feedback are called closed-loop control systems. The feedback is used to make decisions about changes to the control signal that drives the plant. An open-loop control system does not have or doesn't use feedback. It is generally agreed that there are five control modes by which closed-loop servo systems react to errors: on-off control proportional control proportional plus integral control proportional plus derivative control proportional plus integral plus derivative control Supply Disturbance A supply disturbance occurs when the supply to a process changes Demand Disturbance
Process Control Systems Liquid Level Control LAP 7 ON/OFF control: An on-off controller is the simplest form to control an operation. The output from the device is either on or off, with no middle state. An on-off controller will switch the output only when for example the temperature crosses the set point. Deadband (sometimes called a neutral zone or dead zone) is an interval of a signal domain or band where no action occurs. Narrow deadband causes high oscillation, therefore reduces the lifetime of component. Wide deadband reduces oscillation, but has higher error. Electromechanical relay ON/OFF control Program a Honeywell UDI 1700 Process meter’s discrete outputs to control alarms. Use a Honeywell UDI 1700 Process meter to perform ON/OFF control. Closed loop systems: Systems that utilize feedback are called closed-loop control systems. The feedback is used to make decisions about changes to the control signal that drives the plant. An open-loop control system does not have or doesn't use feedback. It is generally agreed that there are five control modes by which closed-loop servo systems react to errors: on-off control proportional control proportional plus integral control proportional plus derivative control proportional plus integral plus derivative control Supply Disturbance A supply disturbance occurs when the supply to a process changes Demand Disturbance