Precision Thermocouple Measurement ADS1118

Precision Thermocouple Measurement with the ADS1118

Thermocouples are a very common form of temperature measurement devices that are widely used in
both industrial and general-purpose applications. Traditionally, achieving high system accuracy from
thermocouple measurements can be difficult because there are many sources of error within a given
system. The ADS1118 is an analog-to-digital converter (ADC) from TI that offers a precision analog
front-end specifically designed for precise measurements of thermocouples. The ADS1118 makes
thermocouple designs simple, and also provides on-chip cold junction compensation. This application note
presents the basic principles of thermocouple operation as well as the real-world implications of these
principles. It reviews both design and layout considerations for achieving a high-accuracy, robust design.
Experimental results for ADS1118 thermocouple measurements and cold junction compensation are
discussed, as well as a recommended software flow that demonstrates how to simplify a lookup table by
using linear interpolation.