This capacitance sensor can take the heat
Rechner
The new KA7000 capacitance sensor (photo) has a temperature rating of 120°C (248°F). Its polyamide housing has a high resistance to abrasion, so operation with granular material is not an issue. The sensor is also not disturbed by high vibrations. The sensor is fully potted, making it water- and dust-tight with IP67 protection. The sensor operates at 12–30 V, has a sensing range of 2 to 25 mm and is suitable for dryer applications. — Rechner Electronics Industries, Inc., Sanborn, N.Y.