I built a solar water heater controller 25 (?) years ago and being cheap and lazy I used diodes for temp sensors to make a differential thermostat. The sensitivity is low, so I just used 5 in series.

New options for health, environmental monitoring with water-resistant gas sensor. ScienceDaily . Retrieved June 2, 2025 from www.sciencedaily.com / releases / 2022 / 08 / 220804130611.htm ...