| 摘要 |
PURPOSE:To display the accurate liquid surface readily with high sensitivity, by providing the reference contact point of a thermocouple in the liquid phase of a low temperature liquified gas, so that the voltage generated by the thermocouple is digitally changed. CONSTITUTION:A current is supplied to a heating resistor body 2 from an external power source 1. The temperature of the body is increased by Joule's heat. A temperature measuring contact point 3 of a thermocouple is thermally contacted with the heating resistor body 2. The change in the height of the liquid phase part of a low temperature liquified gas is detected as the temperature change of the temperature measuring contact point 3. At the liquid surface height h1, e.g., the temperature of the heating resistor body 2 is t2. At this time, the thermocouple generates a voltage V3, which corresponds to the difference between the temprature t2 and the temperature of the liquid phase part of the low temperature liquified gas. At a liquid surface height h2, the temperature measuring contact point 3 and a reference contact point 11 of the thermocouple are both located in the liquid phase part of the low temperature liquified gas. Therefore almost no temperature difference is present, and the generated voltage is almost zero. Thus the digital signal is obtained, and the presence or absence of the liquid surface can be definitely judged. |
