REALIZATION OF 4th ORDER RECURSIVE DIGITAL FILTER WITH PLC CONTROLLER

This paper describes the design and realization of the third and fourth order recursive digital filter (IIR digital filter) using PLC controller. The purpose of the filter is elimination of unwanted signals which occur during processing of analog signals in the industrial process automation with PLC controllers. The Siemens S7-315-2DP PLC controller is used in practical realization. In this application, we chose the eliptical filter with a cut-off frequency of 3 Hz and a sampling frequency of 50 Hz. With format long of the filter coefficients values we obtain the expected stop band attenuation of 40 dB as it is designed with MATLAB software. The values of impulse response are applied to compare PLC controller realization of digital filter and simulated structure with MATLAB.