Integration of Weighing Indicator with Proprietary Commands into PLC-Based System Using Modbus Protocol

This paper presents a technique to integrate a stand-alone weighing indicator with proprietary commands into a monitoring system of industrial production processes. The proposed technique is based on creating a new function block of the programmable logic controller (PLC) used in weighing machine control for converting weighing indicator commands into the Modbus-RTU commands. Creation of the function block operated in the PLC modeled CP1L-M30DR-D for converting commands of the AD-4401 weighing indicator to display on the Panel Master touch-screen monitor is described as an illustrative case study. Based on the proposed method, weighing data at the field site for local readout can be added into process data monitoring at the human machine interface (HMI) station of the PLC-based system. This enables ease of upgrading the weighing machine used, which has weighing indicator with local readout display. Performance of the proposed system integration is verified by experimental results.