TEMPERATURE MEASUREMENT APPARATUS

摘要

TEMPERATURE MEASUREMENT APPARATUS A light source for forming an optical path that extends across a closed vessel and a light receiving unit for receiving light from the light source are disposed outside the vessel. An element to have its temperature measured lies in the vessel and is provided with a temperature detecting device which consists of a temperature sensor and a light intercepting plate. The temperature sensor is formed by sticking two concave members of different coefficients of thermal expansion one over the other. When the element has reached a predetermined temperature, the temperature sensor reverses the concave condition to a convex one. This causes the light intercepting plate to be turned into the optical path to intercept part of the light from the source. Thus, the quantity of light received by the light receiving unit changes, and the temperature of the portion is measured through a light quantity - temperature conversion. Preferably, there are more than one, e.g. three, temperature sensors set to operate at different temperatures and each with a light intercepting plate of different magnitude so that a stepwise indication of the temperature can be obtained.