Isolated and Programmable Temperature Transmitter

A cost effective solution is designed for a typical RTD (resistance temperature detector) and thermocouple temperature transmitter for a 2-wire and 3 wire 4-20mA current loop system. The design leverages integrated analog components and R5F100FCAFP microcontroller. The voltage controlled current source of the transmitter design is enabled by the general purpose operational amplifiers on the device. Biasing of the current source was carried out via a loop control PWM pin and converted in to current source by analog components. 16-bit resolution of input value is achieved by over sampling method. The signal conditioning of the sensed RTD value was carried out via a differential amplifier of incorporating on-chip analog components. Temperature transmitter is transmitting data based on the Modbus (RTU) protocol, Transmitter solution provides further flexibility due to the additional processing enabled by the microcontroller. This allows linearization through software for the display of observed / measured values.