Microcontroller-based temperature monitoring and alarm annunciation system design

Hassanain Ali Bashar
Dr. Mohammed T. Lazim

Abstract : Wide range temperature monitoring and annunciation systems are implemented in many industrial applications and the present work is intended to develop a modern and easy-to-install temperature monitoring system that serves monitoring and annunciation of several nodes. The proposed system uses type-k thermocouples as primary sensing element; the output voltage from the thermocouple is amplified using suitable thermocouple amplifier circuits. The system is intended to measure temperatures in the range from 0 to 1250 °C at two different measuring points. The conditioned output voltages are converted to frequencies corresponding to these levels by using suitable voltage to frequency converter circuit. The frequency is measured using an 8-bit 89C51 microcontroller and is stored in memory. These frequencies represent the temperature information and are transmitted through a two-wire network to a remote microcontroller unit that processes and displays the received data. The implemented two remote nodes to measure the temperature at two different places, and the data are collected from the two units through the two wire network which connects both nodes to the main microcontroller unit. The data are transmitted and received over the network using the RS-485 voltage levels, speeds and protocols. The designed system has been built, tested at the laboratory and the results prove to be successful with specified design requirements. The proposed system is a practical system that can be implemented directly in practical fields to suit given application task due to its advantages, easiness and low cost implementations.