Fibre-optic thermometer or temperature alarm device

A temperature alarm device making use of fibre optics, characterized in that the device comprises

• a fiber-optic light transmitter (1), which sends light along a transmitting optic fiber (2) to a measuring head (5) on the end of the transmitting fiber (2), and
• a fiber-optic receiver (3), which is connected with a receiving optic fibre (4) to the same measuring head (5), and
• the measuring head (5) comprises a cell or hollow enclosure (6) with said transmitting (2) and receiving (4) fibres extending into said cell or enclosure (6) which has been filled with substantially homogeneous light-scattering substance (7) of the kind which below a certain substantially abrupt threshold temperature scatters the incident light from the transmittting fibre (2) back to the receiving fibre (4),
• but above the threshold temperature characteristic for the substance (7), loses its light scattering capacity so that the light coming from the transmitting fibre (2) is no longer scattered to the receiving fibre (4),
• whereby transgression of the threshold temperature characteristic for the substance (7) is observable in the fibre-optic receiver (3) as a diminishing of the back-scattered light and of the signal thereby caused.