Convection heater with electrical resistive heating element - made of specified PTC material with angular position control setting air passage opening

摘要

The heating element can be turned from a position where it greatly reduces the available passage and a position where it mostly clears it. The heater is a PTC termistor which increases its resistance at above the working temp. by at least two orders of magnitude, referred to a temp. difference of 100 deg.C. A frame (2) in a casing (1) has a resistance heater (3) which is angularly adjustable around a pivot (4). This can be done manually or by a servo motor. The max. temp. in calm ambient air is 300 deg.C and the preferred material for the resistance heater is a doped polycrystalline ceramic material, pref. barium titanate. ADVANTAGE - Maintains temp. without having to adjust input and eliminates any overheating. Merely requires re-adjustment of position of element.