THICK FILM HEATER

摘要

An electrical resistance or heater of the type comprising a thick film resistive track provided on an insulating substrate has two predetermined sections of said track (8d, 8e) with a predetermined current carrying capacity. These sections are bridged by a discrete bridge (22) of an insulating material, e.g. glass, which at a predetermined temperature becomes sufficiently conductive to cause a failure current to flow through one or both of said sections (8d, 8e). The resistive track (8) is protected from oxidation by a separate overglaze layer. Also disclosed is such an electrical resistance or heater wherein the track section (8d) passing the failure current is provided with means, such as an aperture (24) in the track, for concentrating locally the current flowing therethrough.