High-performance temperature measurement using thermocouples and precision delta-sigma ADCs, Part 2

This two-part series presents the design of a cost-effective, portable, high-resolution data-acquisition system (DAS) based on a precision delta-sigma analog-to-digital converter (ADC). The Part 1 article reviewed the history of thermocouple technology and the principal of the operation. It described a thermocouple interface with the MAX11200 ADC evaluation (EV) kit.1

This Part 2 of the series presents a dedicated reference design (RD) in which the MAX11200 ADC interfaces with a thermocouple and platinum resistance temperature detector (PRTD) using a simple multiplexor. No additional instrumentation amplifiers, low-noise references, and optical isolation are needed for precise temperature measurement. The new RD is cost effective, compact, and low power. We also describe the high-resolution thermocouple’s DAS and the software required to achieve accuracies of ±1°C, or better, using standardized linearization calculation algorithms.