Abstract: A level measuring device suitable for measuring the level of any substance, advantageously but not necessarily dangerous substances whether due to heat, toxicity or others, with or without anti-oxidization superficial layers, including in mutual cooperation and coordination an intense light source illuminating a limited and restricted area on the surface of the medium whose level is to be measured, a receiver-perceptor processor so arranged that at least part of the optical control axis is at an angle in relation to the incidence optical axis of said light source, therebeing advantageously present one or more regulating means responsive to the ambient light and to possible infrared rays or the like, regulating means responsive to absorption and reflection features of the light by the material of the surface and the medium in which the rays propagate, alarm means and regulation means.

Abstract: A device for controlling the level in a container of a liquid which will emit infra-red rays and particularly molten metal is described. The device comprises a housing, at least one longitudinal window at one end of the housing and arranged so that when in use it will overlook an edge of a container containing the liquid, the level of which is to be controlled; and at least one photo-element for sending out an electrical signal through said window to said liquid; at least one second window which is substantially punctiform and which overlooks a substantially constant portion of the liquid in the container and within the vertical field of adjustment; and a second photo-element in cooperation with the second window for sending out a pilot signal, and circuitry to correct the signal indicating the liquid level of the container by means of the pilot signal and for amplifying and comparing the signal coming from the correction circuit.