| 摘要 |
PROBLEM TO BE SOLVED: To obtain a light quantity necessary for automatic measurement even in the case where smoke is generated and to automatically measure thermal expansion coefficient of a specimen which generates a large quantity of smoke by adjusting the light quantity based on comparative computation of light and darkness digital signals which indicate bright parts and dark parts detected by line sensor cameras. SOLUTION: Two lighting systems 31, 32 illuminate both ends of a specimen 11 through a window formed in an electric furnace 10 and the light is received by two line sensor cameras 41, 42 on the opposite to the lighting systems through a window formed in the electric furnace 10. The cameras 41, 42 are for detecting the shadow of the end parts of the specimen and measuring displacement of the length and the quantities of light from a dark part where light is shield and a bright part where light reaches is converted into electric signals. Opto scales 43, 44 detect and display the converted electric signals as oscillographic waveforms and at the same time the light and dark signals of the dark parts and light parts are converted into digital signals. An automatical light quantity adjusting apparatus 30 compares the digital signals with previously containing standard values and the voltage of the lighting systems 31, 2 are so controlled as to make waveforms of the opto-scales normal and thus light quantity adjustment is carried out. |
