In any Industrial and Commercial applications, Temperature and the Humidity are the important parameters to monitor and control. Sensing the Temperature and controlling them is very important and they must be secured data too and should not get corrupted while transmitting from the field of measurement to the place of controlling. For a long distance of Data communication (up to 2000 meters), the RS485 communication is a cost effective data transmission.In RS485 communication the data transfer is a two wire communication and there are many protocols for Multi node communication. Some of them are MODBUS COMMUNICATION, FIELDBUS COMMUNICATION, PROFIBUS COMMUNICATION. Here in this text book the data is transferred with the MODBUS Protocol. MODBUS is a serial communications protocol published by Modicon in 1979 for use with its programmable logic controllers (PLCs). MODBUS is often used to connect a supervisory computer with a remote terminal unit (RTU) in supervisory control.It has become a standard communications protocol in industry, and is now the most commonly available means of connecting industrial electronic devices.