Design of the Temperature Acquisition Module Based on Field-bus RS485

摘要

The design scheme of the temperature acquisition module based on Field-bus RS485 is presented. The overall design block diagram of the module is given. The measuring and amplifying circuit for thermistor signal, interface circuit for A/D conversion, interface circuit for isolated RS485 and switching power supply circuit are introduced in detail. The quadratic interpolation is used to calculate the temperature value. As the core of the module, the single-chip computer W77E58 makes multi-channel share the A/D conversion, gathers 8 signals from the thermo-resistances via the multi-channel switch, then converts them to temperature values which is transmitted to the industrial computer via the RS485 Field-bus under the mode of MODBUS protocol. This module can be used as the bottom layer module for temperature acquisition in computer control system.