Integrating a PI Heater Into Compact OEM Assemblies
https://electric-heat-insights.clearhavendigest.com/posts/what-is-the-difference-between-a-glass-heater-and-a-flexible-heater
In sensors, a pi heater must deliver heat in a controlled way. It uses a thin resistive foil circuit laminated in polyimide film. One useful trait is fast response. Still, local hot spots can change the result