Liquid Level Measurement and Control using Microcomputer

The paper presents real-time software design methodology and control of liquid-level system using a microcomputer. Basic principles of data acquisition, actuators characterization, computer interfacing with sensors/actuators, and controller tuning of the unknown process model have been discussed. The experimental setup consists of a water tank, capacitance type level sensor and a stepper motor driven needle control valve. The level sensor and stepper motor are interfaced with an IBM compatible PC/XT which has been programmed in TURBO PASCAL Ver 5.0+ to record and control the water level in the tank. The Petri Net (PN) model of computer control system has been developed to provide total real-time tasks and the execution sequence and their interactions. The experimental results have been provided to obtain optimal controller parameters using reaction curve as well as quarter amplitude damping. The closed-loop response is obtained to show the effectiveness of the design methodology.