Design of PLC Based Pressure Control System Using a Low Cost Non-Contact Ultrasonic Type Pressure Transducer

In the present paper, a low-cost non-contact ultrasonic type pressure transducer has been designed and developed, where outputs are changing with the change of pressure and utilised to design a PLC based fluid pressure control system. The output of the proposed ultrasonic type of transducer has been amplified then converted to standard 1 – 5V, DC voltage signal by signal conditioning circuit and transmitted to one of the analog input channels of PLC. A suitable ladder diagram has been designed using the PID functional block. The analog output voltage 1 – 5V, DC of the PLC based PID controller has been sent to the pneumatic control valve [3-15 PSI] to control the pressure in a vessel through the V/P converter. From the static characteristics of the proposed transducer and signal conditioning circuit as well as control loop, it is found that the output voltages of the transducer are linearly related with the pressure with good accuracy, repeatability and the control system using PLC has been found to produce satisfactory result within the tolerable limit of measurement errors.