Implentation of Pi Controller for Level Process using Non Contact Sensor Ch. Sai Vamsi * , Manoj Mohan, Naveen Chandrakar and K. R. Prabhu School of Electrical Engineering, VIT University, Vellore-632014, India; ishupa@gmail.com Abstract The accurate information about the fluid level in the process station is of much significance in order to maintain a desired level in the process tank by controlling the process through various controllers as the primary objective of all the indus- tries is to maintain the level at desired set points in spite of the external disturbances. The contact type sensors which are used for sensing the level in the process tank usually gets afected by corrosion which results in reduced life span of sensor and in-turn gives a poor and in-efficient performance, and also loss of accuracy in determination of the fluid level. The use of non contact type sensor will be greatly useful in finding the fluid level in the process tank and helps in calculating the error with regard to the desired level and helps in controlling the level by means of the PI controller. The use of PI control- ler would result in maintaining accurate desired level by removing the ofset error. Therefore the ultrasonic transceiver which in this case used as a non contact level sensor would have a good life span as compared to the contact type sensor by reducing the efects of corrosion to a minimum level. Keywords: Process Tank, PI Controller, Ultrasonic Transceiver, Ofset Error 1. Introduction Te level process can be controlled by using PI (Proportional Integral) controller by detecting the level in the process tank using non contact sensor (ultrasonic transceivers). Te level control plays a prominent role in many industries for the efective operation of plant. Te use of contact type sensors would detect the level in process tank but as the life span of the contact type sensor decreases due to the afects of corrosion, they are not much prominent to the industries. Te use of non- contact sensors in the place of contact type sensors would give the level for usually a long span of time. Te level in process tank can be controlled by implanting PI control- ler along with the ultrasonic transceivers. Te level data thus obtained from the ultrasonic sensor is used to obtain the error by comparing it with the desired set point fuid level. Te ultrasonic sensor is interfaced with arduino as per the specifcations of the process tank where the level is to be controlled. Te error that is obtained gets processed by means of a PI control algorithm which is programmed in the arduino. Afer the compilation of the PI control algorithm in arduino the output of PI controller is fed to the pres- sure control valve by means of a pressure transducer and voltage to current converter which controls the fuid inlet fowing into the tank by closing and opening the valve to a required level. As there is a variation in the level the error varies and it gets fed to the input port in arduino which is further used in PI control algorithm in arduino. As the control signal which we get in the controller output is a voltage signal, it should be converted to the equivalent current signal using voltage to current converter, since the pressure transmitter receives current signal. Tus the cur- rent signal is converted to the pressure signal by pressure transducer which is fed to the pressure control valve in order to control inlet fuid fow in to the tank. Te actual process station is shown in above fgure. 2. Sensor Operation Te liquid level sensing is done by using an ultrasonic transceiver (HC-SR04) which we used as a no-contact level sensor for determining the fuid level in the level Indian Journal of Science and Technology, Vol 8(S2), 36–39, January 2015 *Author for correspondence ISSN (Online) : 0974-5645 ISSN (Print) : 0974-6846 DOI: 10.17485/ijst/2015/v8iS2/59231