How to Maintain Wafer Heater for Stable Day-to-Day Heating
https://thin-film-heating.evergrovio.com/posts/how-to-test-a-semiconductor-heater-for-safe-and-consistent-performance
Many heating problems look like a power problem at first. In practice, the cause may be contact, heat loss, sensor position, or poor fit. A wafer heater works best when these parts are planned together