How to Maximize Temperature Measurement Accuracy

Thermocouples are the most versatile and widely used devices for temperature measurements. They are inexpensive, reliable, rugged, and can be used over a wide temperature range. These sensors require cold junction compensation and complex linearization algorithms to achieve good accuracy. The output voltage of thermocouples is very small (tenths of mV) and hence require high gain amplifiers before being fed to the ADC. Any errors and non-linearity in these areas of signal conditioning and amplification will lead to inaccurate measurements. Most test engineers are careful about the measurement errors caused by thermocouples, but not always about the measurement system. Measurement systems are calibrated regularly (typically once per year) at ambient room temperatures and are expected to perform throughout the year with the same accuracies.