| 摘要 |
The present invention provides a level detector to sense whether the level of a liquid having a nonambient temperature such as a cryogenic liquid has reached a predetermined point. A stainless steel type T thermocouple probe is provided for generating a temperature signal referrable to absolute temperature. The type T thermocouple probe is adapted to be mounted so that it submerges in the liquid when the level of the liquid has reached the predetermined point. A high thermal conductivity tube is, at one end, in good thermal contact with a thermocouple contained within distal end of the thermocouple probe and, at the other end, is exposed to ambient conditions. The high thermal conductivity tube acts to conduct heat between the ambient and the thermocouple. A thermally insulating tube encapsulates the copper tube between its ends so that heat is not dissipated along its length and the temperature signal will be a function of a sum of the nonambient temperature of the liquid and a constant divided by a convective heat transfer, which will increase in the liquid. As a result, the temperature signal will change upon submergence of the thermocouple within the liquid to indicate that the liquid has reached the point level detector. <IMAGE> |
