without optical isolation and dedicated reference Figure 2.Block diagram of the MAX11200 DAS-based temperature measurement system. Design allows dynamic measurement of either the thermocouple or PRTD.

A Thermocouple is a terrific way to measure temperature. The effects of temperature change on dissimilar metals produces a measurable voltage. But to make that measurement you need an amplifier ...

This is because of how it integrates not only the tip and heating element, but also a thermocouple ... diagram [Clive] explains how these T12 elements are then used to regulate the temperature ...