| 摘要 |
PURPOSE:To obtain an economical liquid helium levelmeter by applying a pulse current to a heater to renew the liquid when the heater is turned OFF. CONSTITUTION:A DC constant current I1 for measurement is always applied to a super conductive conductor 1 from a constant current source 3. As the conductor 1 reaches the normal conduction state, the resistance value is by far smaller than that of a heater 2, the heat generated in the conductor 1 is very much smaller than that by the heater 2. On the other hand, a pulse current I2 is applied to the heater 2 at a fixed cycle from a pulse generation circuit 12. Then, the ON time (T1) of the heater is set enough to always energize the part B of the conductor 1 and the temperature at the part B will exceed the critical point within the time T1 by a Joule heat to accomplish the invariable conduction of the part B, which nulifies the measuring errors of the liquid 9 to ensure accurate measurement. The OFF time (T2) of the heater 2 is determined taking into account of the sampling cycle of a liquid level measuring system and the time in noway disturbing the measurement in the practical use. When the heater 2 is turned OFF, the liquid level of a display 13 with a memory is renewed. |
