PURPOSE: To enable self-test for leakage of sealing liquid and entrance of hydrogen gas into the sealing liquid without removing a differential pressure measurement device from measurement line by providing a storage circuit which stores output from a differential pressure detection part.
CONSTITUTION: A high pressure side pressure introduction pipe 23 introduces the pressure of the upstream side of a orifice 22 and a low pressure side pressure introduction pipe 25 introduces that of the downstream side of the orifice 22, respectively, to a differential pressure detection part 24, and, the detection part 24 detects pressure and temperature conveyed through the pressure introduction pipes 23 and 25. A storage circuit 30 stores the outputs from the detection part 24 when excessive pressure is applied to one side of a seal diaphragm and atmospheric pressure to the other side, and when excessive pressure is added to the other side of the seal diaphragm and atmospheric pressure to one side. At the time of self-test, in a diagnosis circuit 33, for example, the output from the detection part 24 when the excessive pressure is applied to the high pressure side and the atmospheric pressure to the low pressure side, and the output from the detection part 24 when, after that, the excessive pressure is applied to the high pressure side and the atmospheric pressure to the high pressure side, are compared to a stored value in the storage circuit 30. So that, leakage, etc., of sealing liquid is decided.
KUWAYAMA HIDEKI
TOYODA SHOJIRO
KANEHIRA ATSUKO
